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MAGISKA MOLEKYLERS WIKI |
Cannabis och fortplantning
Innehåll
Cannabis ger minskad sexlust
I förbudsförespråkarnas klassiska bibel "Haschboken" kan man läsa att cannabis ger minskad lust att inleda förhållanden:
| “ | De som röker hasch regelbundet blir alltid förändrade. Det börjar med att de blir lättirriterade, slöa och tillbakadragna. Fortsätter missbruket blir de mer och mer inneslutna i sig själva och till slut hamnar de i ett stadium där de är känslomässigt störda — de struntar i stort sett i allt. De bryr sig inte om att arbeta eller plugga, hygienen skjuts åt sidan och de blir allt mer ointresserade av kontakter med det motsatta könet. — Haschboken (1994)[1] |
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Och i Drugnews faktasektion om cannabis påstås drogen leda till dämpad sexlust[2]. Påståenden om minskad sexlust eller avstannat sexliv är en vanlig missuppfattning som med jämna mellanrum återkommer i så kallade faktablad från svenska förbudsförespråkare, ibland tillsammans med påståenden om sterilitet, fosterskador och liknande. Det är lite märkligt då den första generationens propaganda från 1930-talets USA menade att "marihuana" tvärtom gjorde brukaren galen av åtrå och det ledde till oanständiga sexuella förbindelser, våldtäkter och utomäktenskapliga graviditeter.
Tittar man på forskning på området så har cannabisanvändare (både män och kvinnor) mer sex än ickeanvändare[3][4]
| “ | In all, Eisenberg and Sun obtained data on 28,176 women averaging 29.9 years of age and 22,943 men whose average age was 29.5. They assessed these individuals’ self-reported patterns of marijuana use over the previous year and their self-reported frequency of heterosexual intercourse over the previous four weeks.
Some 24.5 percent of men and 14.5 percent of women in the analysis reported having used marijuana, and there was a positive association between the frequency of marijuana use and the frequency of sexual intercourse. This relationship applied to both sexes: Women denying marijuana use in the past year, for example, had sex on average 6.0 times during the previous four weeks, whereas that number was 7.1 for daily pot users. Among men, the corresponding figure was 5.6 for nonusers and 6.9 for daily users. In other words, pot users are having about 20 percent more sex than pot abstainers, Eisenberg noted. |
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Cannabis gör dig steril
Män
Spermier har cannabinoidreceptorer som normalt binder endogena cannabinoider (anandamid och 2-AG). Cannabinoiderna från Cannabis kan också binda till receptorerna och förändringar spermiernas uppgifter. Forskning (främst från Schuel) under 1980 och 1990-talet visade forskare att cannabinoider binder sig till Sjöborrars spermier och hindrar akrosomreaktionen (när spermien tränger in i ägget)[6][7][8].
Hall sammanfattar forskningarna i en metastudie från 2001:
| “ | Studies conducted in the mid-1970s showed that animals given large doses of cannabis or THC during pregnancy had lower levels of the gonadal hormones (testosterone and oestrogen) that control reproduction (1–5). There were also case reports of breast development in young men who had a history of heavy cannabis use (6). A study by Kolodny et al (7) found that chronic male cannabis users had lower levels of testosterone, a lower sperm count and motility, and more abnormal sperm than controls. These observations raised concerns that the use of cannabis by young adults during the 1970s and 1980s would impair fertility in men and adversely affect pregnancy outcomes in women.
... Male animals given large doses of cannabis, crude cannabis extracts, THC and other cannabinoids showed lowered testosterone levels, retarded sperm maturation, reduced sperm count and sperm motility, and increased rates of abnormal sperm (1, 5, 9, 10). Although the mechanisms for these effects were uncertain, it was likely that they were a direct effect of THC on the testis, and an indirect effect on the hypothalamic hormones that stimulate the testis to produce testosterone (5). Human studies of the effects of cannabis on male reproductive function produced mixed results (9). The study by Kolodny et al (7), which reported reduced testosterone, sperm production, and sperm motility and increased abnormalities in sperm, was not replicated in a larger, better controlled study of chronic cannabis users. This study failed to find any difference in testosterone level at study entry, or after three weeks of daily cannabis use (11). The significance of the animal findings for human cannabis users are uncertain (2) because testosterone levels in human cannabis users have generally been within the normal range (12). |
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2003 visade forskare att cannabisrökande män har mindre mängd sädesvätska och lägre antal spermier. Man kunde även se att spermierna simmade för snabbt, vilket ledde till att energin tog slut i förtid.
| “ | In the current study, Burkman received seminal fluid from 22 confirmed marijuana smokers and subjected the samples to a variety of tests. The volunteers reported smoking marijuana approximately 14 times a week, and for an average of 5.1 years.
Control numbers were obtained from 59 fertile men who had produced a pregnancy. All men abstained from sexual activity for two days before the lab analysis. ... "The sperm from marijuana smokers were moving too fast too early," said Burkman. "The timing was all wrong. These sperm will experience burnout before they reach the egg and would not be capable of fertilization." Burkman noted that many men who smoke marijuana have fathered children. "The men who are most affected likely have naturally occurring borderline fertility potential, and THC from marijuana may push them over the edge into infertility," she said. |
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Se även forskningsresultat från Burkman och Schuel[11][12].
Men man kan även notera att det finns studier som visar att män som röker eller har rökt cannabis har högre antal spermier än personer som aldrig rökt alls. En studie från 2019 visar att det är mer än dubbelt så många av ickerökarna som har antal under det normala än det är bland personer som röker cannabis[13][14][15].
2006 undersökte forskare mänskliga spermiers rörlighet efter att doserat spermierna med THC och märkte en klar minskning av rörligheten[16].
| “ | The study by the Reproductive Medicine Research Group discovered that THC impedes sperm motility making it less likely that the sperm will reach the egg to fertilise it. And that another key function of the sperm – to digest the egg's protective coat with enzymes in a bid to aid sperm penetration – is impaired in the presence of cannabis.
Fifty-one semen samples were used, split, and treated with THC or simply incubated as a control. THC-treated samples were found to be up to 45% less forward moving and up to 30% of THC-treated sperm don’t release the enzymes needed to penetrate the egg. |
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En studie från 2012[18] där möss fick dricka cannabis upplöst i mjölk (bhang) stödjer påståenden om minskat antal spermier och minskad livskraftighet och rörlighet.
En studie från 2015[19] där man undersökte sperman hos 1215 unga danska män visade att cannabisrökare som rökte en gång i veckan eller oftare hade 28% mindre spermiekoncentration och 29% mindre antal spermier.
Forskning från 2010[20] har även visat att CB1 och CB2-receptorer påverkar spermiers rörlighet och en studie från 2016[21] visar att regleringen av CB2-receptorerna kan vara anledningen till minskad spermieproduktion. Både över och understimulering av CB2 försämrar skapandet av nya spermieceller.
Det finns således gott om bevis för att cannabis påverkar både spermiernas antal och rörlighet (motalitet) negativt. Men vilken betydelse har cannabis för genomsnittskonsumenten förmåga att skaffa barn? Förmodligen är den inte avgörande eller ensam faktor för någon människa, eftersom världen är full av olika kemikalier och andra orsaker som kan inverka och samverka.
Man har exempelvis konstaterat att hög konsumtion av Kaffe eller Coca-cola försämrar spermakvaliteten[22] och t.o.m påverkar dess DNA[23]. Tobak och alkohol minskar också spermiernas antal, men man har sett att cannabinoider kan minska den effekten hos tobaksrökande män[24][25].
Kostens inverkan på spermiernas antal och rörlighet har studerats av många forskare och det finns många rekommendationer om vilken kost som inverkar positivt respektive negativt[26]. Det finns exempelvis forskning som visar att isoflavoner i sojabönor halverar spermiekoncentrationen även om man bara äter en halv portion om dagen[27][28]. Resultatet är bara ett i ledet av sterilitetsvarningar gällande sojabönor som är vanligt förekommande i halvfabrikat, vegankost m.m.[29]. Det finns metaanalyser som hävdar motsatsen[30], men även nyare studier bekräftar att vegetarianer har sämre spermakvalitet än ickevegetarianer[31]. Här kan man få intrycket att man skall äta mycket kött, men det är inte heller bra om det är processat (korv, hamburgare etc.) vilket forskning från 2014 indikerar[32][33]. Konsumtion av ost och mjölkprodukter leder också till sämre spermieproduktion enligt en studie från 2013[34]. Fisk och inälvsmat verkar dock vara bra.
Väldigt många spermier har dålig kvalitet hos de generationer som skaffar barn nu bland oss nordbor. Antalet spermier har nästan halverats sedan 1940-talet enligt danska studier. Och då ska man tänka på att endast 5 - 15 % av människospermierna anses ha tillräckligt bra kvalitet att kallas "normala" enligt WHO:s krav.
En av de största faktorerna för låg fertilitet är tyvärr omöjlig att påverka, eftersom den uppstod i mannens fosterstadie och beror på hans mammas kost:
| “ | A man who smokes typically reduces his sperm count by a modest 15 per cent or so, which is probably reversible if he quits. However, a man whose mother smoked during pregnancy has a fairly dramatic decrease in sperm counts of up to 40 per cent – which also tends to be irreversible.
... The number of sperm that can be produced in an adult man is critically dependent on the number of Sertoli cells that develop in his foetus, so anything that interferes with the formation of Sertoli cells in a mother's womb will affect sperm production many years later. "Maternal-lifestyle factors in pregnancy can have quite substantial effects on sperm counts in sons in adulthood, and the most logical mechanism by which this could occur is via reducing the number of Sertoli cells," Professor Sharpe says. |
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Värme är också en stor faktor som minskar spermiernas antal och motalitet. Det gäller allt från att sitta i varma bilstolar till att ta varma bad. En studie från 2007[36] visade hälften av männen i studien ökade antalet spermier med 491% efter att de slutat med varma bad.
Män som cyklar mer än 5 timmar i veckan har enligt en studie från 2010[37] dubbelt så hög risk att ha låg spermakvalitet än personer som inte cyklar. Andra studier har visat att personer som cyklar riktigt mycket har en stor andel spermier med defekt utseende.
Men man kan konstatera att världen är full av barn vars pappor rökte cannabis innan och under tiden för befruktningen, precis som att korvälskare, sojaätande vegetarianer och elitcyklister också får barn. Det finns ingen alarmerade anledning att nämna cannabis i samma sammanhang som sterilitet även om den påverkar fertiliteten negativt. Effekten kan knappt ens jämföras med ett P-piller då cannabis inte ger en fullständig hämning av spermieproduktionen, men är på samma sätt övergående om man slutar.
Om man har svårt att få barn bör mannen lägga av med alla droger (lagliga och olagliga) en tid innan den högsta fertilitetspunkten i kvinnans menstruationscykel, samt även tänka på alla andra bidragande faktorer (kost, värme, åtsittande kläder, cykling, etc.). Observera att Burkman även skriver om att cannabinoider i slidsekretet kan fästa sig i spermierna och på så sätt framkalla samma negativa effekt, därför är en avhållsamhet från båda könen är att rekommendera.
Kvinnor
När man har studerat sambandet mellan cannabis och fertiliteten hos kvinnor visade det sig att de som rökte minst cannabis var minst fertila:
| “ | In animal studies cannabis and THC interfere with the hormones controlled by the hypothalamic-pituitary-gonadal axis in non-pregnant female animals (1), delaying oestrous and ovulation (9). There have been very few human studies of the effects of cannabis on the female reproductive system because of fears that cannabis use may produce birth effects in women of childbearing age (13). An unpublished study by Bauman (1980 cited by Nahas (3)) compared the menstrual cycles of 26 cannabis smokers with those of 17 controls and found a higher rate of anovulatory cycles among the cannabis users. Mendelson and Mello (14) failed to find that cannabis use affected the female sex hormones, or the duration of the cycle. Mueller, Daling, Weiss and Moore (15) reported a modest association (OR 1.7) between cannabis use and infertility in a case-control study of 150 women with primary anovulatory infertility and 150 controls. The relationship was strongest in women who had used cannabis less frequently. In the absence of any other human evidence, Bloch (1), the Institute of Medicine (2) and Murphy (9) have argued that the animal evidence suggests that cannabis use probably inhibits human female reproductive function but it is uncertain how large these effects are. — The health and psychological effects of cannabis use, Hall (2001)[9] |
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När man sätter detta i perspektiv så har forskning visat att koffein minskar fertiliteten hos möss[38] och ökar risken för missfall hos människor[39].
Cannabis skadar foster under graviditeten
Först några källor som visar hur argumenten används av Svenska "experter" och myndigheter:
| “ | Slutligen orsakar vanemässigt cannabismissbruk under graviditeten lägre födelsevikt hos barnet och tycks också ge skador på barnets centrala nervsystem. — Karolinska Institutet[40] |
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| “ | Cannabis och graviditet
— Kerstin Käll Med.dr., överläkare Beroendekliniken Universitetssjukhuset Linköping[41] |
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| “ | Hormonbalansen kan störas, både hos män och kvinnor. Hos ungdomar kan detta hindra att kroppen utvecklas normalt. Produktionen av det manliga könshormonet testosteron kan minska och den sexuella lusten försämras. Hos kvinnor kan de hormoner som styr ägglossningen förändras och menstruationscykeln kan rubbas, vilket kan påverka fruktsamheten. Vidare löper barn till mödrar som använder cannabis under graviditeten ökad risk att födas underviktiga. — CAN Drogfakta[42] |
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| “ | I en metaanalys av tio observationsstudier fann man ingen effekt på födelsevikten om modern använt cannabis under graviditeten [11]. Övergående irritabilitet har observerats under nyföddhetsperioden när modern använt cannabis [13]. Störd nattsömn kvarstod fram till under-sökningen vid tre års ålder hos barn vars mödrar missbrukat cannabis under graviditeten [8]. I en longitudinell och multifaktoriell studie från Pittsburgh med 763 barn från familjer med låg socioekonomisk status fann man ett samband mellan exposition för cannabis före födseln och hyperaktivitet, uppmärksamhetsproblem och impulsivitet vid tio års ålder [14]. Detta samband kvarstod även när man korrigerat för ett stort antal andra tänkbara riskfaktorer. Behandlingsstudier som inriktats mot cannabismissbruk under graviditet saknas. — SBU - Statens beredning för medicinsk utvärdering (2001)[43] |
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Läs även en kritisk sammanfattning av all forskning från två doktorer, publicerad i Mothering Magazine 2005: [44]
Lägre födelsevikt
Thomas Lundqvist refererar 2003 till Hall att en förmodad negativ effekt är
| “ | ...en ökad risk för låg födelsevikt hos barn till mödrar som har använt cannabis under graviditeten — Thomas Lundqvist[45] |
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Och det är just vad den är. Förmodad. Ej bevisad. Den kan synas i statistiken men försvinner om man tar hänsyn till diverse andra faktorer, exempelvis om mamman har rökt tobak.
Ramström gräver inte heller ner sig så djupt i frågan utan kommer att ägna mer text åt fosterskadorna.
| “ | Påverkan på födelsevikt med mera
Fram till mitten av 1980-talet rådde osäkerhet inom det här området. Tidigare studier gav växlande resultat och var inte alltid tillräckligt noggrant genomförda. En rad senare studier har visat att cannabisrökning under graviditet är statistiskt relaterat till en genomsnittligt lägre födelsevikt (Hatch & Bracken, 1986; Zuckerman, et al., 1989) och kortare kroppslängd (Zuckerman, et al., 1989; Tennes, et al., 1985). Det har dock rapporterats resultat från en multicenterstudie som i vissa avseenden ifrågasätter såväl effekten av både kokain och marijuana på födelsevikten (Shiono, et al., 1995). I denna undersökning finner man inget signifikant samband mellan marijuanarökning under graviditeten och lägre födelsevikt hos barnet. Undersöker man enbart sambandet mellan de mödrar som visat sig ha marijuana i blodet under graviditeten och barnens födelsevikt finns dock en tydlig tendens som pekar i samma riktning som de ovan nämnda undersökningarna. Den samlade bilden är – när hänsyn också tas till undersökningarnas kvalitet, sätt att fastställa pågående missbruk och urval av undersökta gravida kvinnor – att i varje fall vanemässigt cannabisbruk under graviditeten riskerar att påverka graviditeten och fostret med minskad vikt och kortare kroppslängd vid födelsen som följd. Vilken betydelse detta har för barnens fortsatta utveckling vet man dock inte. Det centrala är att man visat att THC genom påverkan på moderns hormonsystem (och förkortat havandeskap) eller genom direkt toxisk påverkan ger en så tydlig och mätbar effekt på fostrets utveckling. |
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Forskaren Wayne Hall och hans kollegor tar upp negativa effekter med cannabis i en rapport från 1994. I stycket om reproduktion kan man läsa att:
| “ | Cannabis use during pregnancy probably impairs foetal development, leading to smaller birthweight, perhaps as a consequence of a shorter period of gestation. It is possible although far from certain that cannabis use during pregnancy produces a small increase in the risk of birth defects as a result of exposure of the foetus in utero. Prudence suggests that until this issue is resolved, we should err in the conservative direction by recommending that women not use cannabis during pregnancy, or when attempting to conceive (Hollister, 1986). — The health and psychological consequences of cannabis use, Hall (1994)[47] |
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I den uppdaterade revisionen från 2001 dämpar Hall den tidigare oron för fosterdefekter och problem med fortplantningen:
| “ | Reproductive effects
Chronic administration of THC disrupts male and female reproductive systems in animals, reducing testosterone secretion, and sperm production, motility, and viability in males, and disrupting the ovulatory cycle in females. It is uncertain whether cannabis use has these effects in humans because of the inconsistency in the limited literature on human males, and the lack of research in the case of human females. There is uncertainty about the clinical significance of these effects in normal healthy young adults. It is likely that cannabis use during pregnancy impairs foetal development, leading to smaller birthweight, perhaps as a consequence of shorter gestation, and probably by the same mechanism as cigarette smoking. There is no clear evidence that cannabis use during pregnancy increases the risk of birth defects as a result of exposure of the foetus to cannabis in the uterus. There is some evidence that infants exposed to cannabis in the uterus may show transient behavioural and developmental effects during the first few months after birth. These effects are small by comparison with those caused by tobacco use during pregnancy, and have not been observed in all studies. |
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En metaanalys från 1997 där 10 studier med totalt 32483 födslar ingick undersöktes ledde till slutsatsen att man inte kan bevisa att cannabis leder till låg födelsevikt. Professor English anser bl.a att tidigare studier som visat samband inte tagit hänsyn till tobaksanvändning, något som är relevant då cannabis ofta intas tillsammans med tobak. Studierna i fråga är Greenland (1983), Witter & Niebyl (1990), Hayes (1991), Castro (1993), Yawn (1994), Singer (1994) English noterar även att studierna inte visar något samband mellan brukets omfattning och vikten, dvs att mer THC för modern ger lägre vikt hos barnet.
| “ | SETTING:From the Medline database, we identified 10 studies in which the results were adjusted for cigarette smoking. In seven studies, information on cannabis use was collected prenatally. Five studies reported results for differences in mean birth weight associated with maternal cannabis use.
PARTICIPANTS: 32,483 women giving birth to live-born infants. MEASUREMENTS: Mean birth weight and odds ratio for low birth weight. FINDINGS: Three analyses of the studies on mean birth weight were conducted to avoid double-counting women from one study. The largest reduction in mean birth weight for any cannabis use during pregnancy was 48 g (95% confidence interval (CI) 83-14 g), with considerable heterogeneity among the five studies. Mean birth weight was increased by 62 g (95% CI 8 g reduction-132 g increase; p heterogeneity 0.59) among infrequent users (< or weekly) whereas cannabis use at least four times per week had a 131 g reduction in mean birth weight (95% CI 52-209 g reduction; p heterogeneity 0.25). From the five studies of low birth weight, the pooled odds ratio for any use was 1.09 (95% CI 0.94-1.27, p heterogeneity 0.19). CONCLUSIONS: There is inadequate evidence that cannabis, at the amount typically consumed by pregnant women, causes low birth weight. |
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Det finns även en stor studie från 1999 som inte nämns. Danska forskare kontrollerade data för nästan 13000 födslar där mammorna hade fått fylla i hälsoformulär och man kunde först se att nyfödda vägde mindre och var kortare hos cannabisrökande kvinnor. När man justerade för alkoholanvändning så fanns avvikelsen kvar, men när man justerade för tobak så försvann den. Det visar att sambandet mellan cannabis och låg födelsevikt inte enbart kan skyllas på cannabis utan andra, tidigare förbisedda faktorer, men i flera fall just tobak.
| “ | In two Copenhagen University hospitals 12,885 pregnant women, seen during the period 1.8.1992 to 30.04.1995, answered questionnaires regarding consumption of alcohol, tobacco, cannabis and other drugs. The prevalence of cannabis use was 0.8%. Women using cannabis but no other illicit drugs were each retrospectively matched with four randomly chosen pregnant women in the same period and the same age group and with same parity. Eighty-four cannabis users were included. These women were socioeconomically disadvantaged and had a higher prevalence of present and past use of alcohol, tobacco and other drugs. No significant difference in pregnancy, delivery or puerperal outcome was found. Children of women using cannabis were 150 g lighter, 1.2 cm shorter and had 0.2 cm smaller head circumference than the control infants. Controlling for the child's sex and maternal use of alcohol did not eliminate the significant differences in birthweight and length; however, they were eliminated by controlling for maternal tobacco smoking. It is concluded, that the use of cannabis is not a major prognostic factor regarding the outcome of pregnancy, but is an indicator of low socioeconomic status and use of other substances. — Cannabis and pregnancy av Balle J, Olofsson MJ, Hilden J (1999)[49] |
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EMCDDA sammanfattar forskningsläget 2008. Man nämner inte resultatet från den danska undersökningen som citeras här ovan men man skriver att eventuella cannabisorsakade skador är låga i jämförelse med vad man ser med tobak:
| “ | The results of research studies on the effects of prenatal cannabis use and birth outcome have been small and inconsistent. Some studies have suggested that cannabis smoking in pregnancy may reduce birth weight. Controlled studies, including a recently reported study analysing the records of live births in New South Wales hospitals over a 5-year period, found that this relation remained after controlling for any confounding variables, although this relation has not always been found in other studies (Zuckerman et al., 1989; Joy et al., 1999; Burns et al., 2006). The effects of cannabis smoking where an association has been found are small compared with tobacco (Fried et al., 1998). There is some evidence that gestation is shorter, especially for adolescent mothers (Cornelius et al., 1995; English et al., 1997; Burns et al., 2006). The relative contributions of smoking and THC are not known from the evidence available. Large, well-controlled epidemiological studies have found no evidence that cannabis causes birth defects (Zuckerman et al., 1989). — EMCDDA, 2008[50] |
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En amerikansk studie från 2010 där 5871 mödrar deltog kommer till slutsatsen att cannabis inte påverkar födelsevikten eller orsakar för tidig födsel:
| “ | RESULTS: The prevalence of reported illicit drug use during pregnancy was 3.6% (standard error 0.24). Pregnant users of cannabis, cocaine, and stimulants were younger, had a lower level of education and lower household income, and were less likely to have used folic acid in the periconceptional period than nonusers. Illicit drug users were also more likely to have used alcohol and tobacco. After adjustment for confounding, cannabis use was not associated with mean birth weight or gestational age or with low birth weight or preterm delivery.
CONCLUSION: Women who report use of illicit drugs during pregnancy differ in demographic and socioeconomic background from nonusers. Reported cannabis use does not seem to be associated with low birth weight or preterm birth. |
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Man kan även notera att sambandet mellan droger och låg födelsevikt är vanligt förekommande, exempelvis har man i studier sett att kaffedrickande kvinnors barn väger mindre[52] och det redan vid motsvarande två koppar kaffe per dag[53].
Missbildningar
Ramström om diverse fosterskador:
| “ | Tidigare forskningsresultat är något motsägelsefulla. Det finns några undersökningar (t.ex. Linn, et al., 1983) som talar för ökad missbildningsrisk, men de flesta och mest välgjorda undersökningarnas resultat motsäger en ökad risk för missbildningar av kroppsdelar eller inre organ vid rökning av cannabispreparat (Zuckerman, et al., 1989).
För fem år sedan tyckte jag att följande resonemang var rimligt: Eftersom det a) finns undersökningar där man kommit till andra resultat, b) de ”friande” undersökningarna har vissa metodologiska brister, och c) flertalet av de ”friande” undersökningarna gäller marijuana och är gjorda under 1980-talets första hälft eller tidigare – då marijuana med låg koncentration fortfarande var vanligt förkommande – skulle det vara oklokt att utesluta cannabis som en orsak till missbildningar innan större och bättre kontrollerade undersökningar har genomförts (Hall, et al., 1994). År 2004 rapporterade L.J. Williams och medarbetare om en omfattande studie över kopplingen mellan ventrikelseptumdefekter (hjärtfel med ofullständig kammarvägg) hos nyfödda och mödrarnas livsstil bland annat i fråga om rökning av marijuana. Bakgrunden var att man under de gångna 30 åren sett en signifikant ökning av denna missbildning i USA. För cannabisrökande mödrar var risken att föda ett missbildat barn fördubblad. Risken ökade med rökningens intensitet. Missbildningar på grund av cannabisorsakade kromosomskador Missbildningar kan också framkallas på annat sätt än genom toxisk påverkan direkt på fostret. Gifter med förmåga att påverka arvsanlagen kan genom att skada an lagen hos någon av föräldrarna framkalla missbildningar på genetisk väg. Man har inte kunnat visa att THC har sådana egenskaper och risken har avvisats i flera forskningsöversikter (Marijuana and Health, 1982; Hollister, 1986; Hall, et al., 1994). |
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Hall skriver i sin rapport från 1994 om svårigheterna att identifiera faktorer som ger falska svar:
| “ | The animal evidence indicates that in sufficient dosage cannabis can "produce resorption, growth retardation, and malformations" in mice, rats, rabbits, and hamsters (Bloch, 1983, p406). Growth esorption and growth retardation have been more consistently reported than birth malformations (Abel, 1985). There are also several caveats on the evidence that cannabis increases rates of malformations. The doses required to reliably produce malformations have been very high (Abel, 1985), and such effects have been observed more often after the administration of crude marijuana extract than pure THC, suggesting that other cannabinoids may be involved in producing any teratogenic effects. There have also been doubts expressed about whether these teratogenic effects can be directly attributed to THC. Some have argued, for example, that the malformations may be a consequence of reduced nutrition caused by the aversive properties of the large doses of cannabis used in these studies (Abel, 1985; Bloch, 1983).
Hollister (1986) has also discounted the animal research data, arguing that "virtually every drug that has ever been studied for dysmorphogenic effects has been found to have them if the doses are high enough, if enough species are tested, or if treatment is prolonged" (p4). Similar views have been expressed by Abel (1985) and by Bloch (1983), who concluded that THC was unlikely to be teratogenic in humans because "the few reports of teratogenicity in rodents and rabbits indicate that cannabinoids are, at most, weakly teratogenic in these species" (p416). ... Even when large sample sizes have been obtained, there are difficulties in interpreting any associations found between adverse pregnancy outcomes and cannabis use. Cannabis users are more likely to use tobacco, alcohol and other illicit drugs during their pregnancy. They also differ from non-users in social class, education, nutrition, and other factors which predict an increased risk of experiencing an adverse outcome of pregnancy (Fried, 1980, 1982; National Academy of Science, 1982; Tennes et al, 1985). These sources of confounding make it difficult to unequivocally attribute any relationship between reproductive outcomes and cannabis use to cannabis use per se, rather than to other drug use, or other variables correlated with cannabis use, such as poor maternal nutrition, and lack of prenatal care. Sophisticated forms of statistical control provide the only way of assessing to what degree this may be the case, but its application is limited by the small number of cannabis smokers identified in most studies. Given these difficulties, and the marked variation between studies in the proportion of women who report cannabis use during pregnancy, the degree of agreement between the small number of studies is more impressive than the disagreement that seems at first sight to such be a feature of this literature. There is reasonable consistency (although not unanimity) in the finding that cannabis use in pregnancy is associated with foetal growth retardation, as shown by reduced birth weight (e.g. Gibson et al, 1983; Hatch and Bracken, 1986; Zuckerman et al, 1989), and length at birth (Tennes et al, 1985). This relationship has been found in the best controlled studies, and it has persisted after statistically controlling for potential confounding variables by sophisticated forms of statistical analysis (e.g. Hatch and Bracken, 1986; Zuckerman et al, 1989). Uncertainty remains about the interpretation of this finding. Is it because the "marijuana products were toxic to foetal development", as argued by Nahas and Latour (1992)? Is it because THC interferes with the hormonal control of pregnancy shortening the gestation period, as has been reported by Gibson et al (1983) and Zuckerman et al (1989)? The fact that the lower birth weight among the children of women who used cannabis disappears after controlling for gestation length is supportive of the latter hypothesis. Is it because cannabis is primarily smoked, since tobacco smoking has been consistently shown to be associated with reduced birth weight (Fried, 1993)? The findings on the relationship between cannabis use and birth abnormalities are more mixed, and conclusions accordingly less certain. Early case reports of children with features akin to the Foetal Alcohol Syndrome born to women who had smoked cannabis but not used alcohol during pregnancy (e.g. Milman, 1982, p42) suggested that cannabis may increase the risk of birth defects. Subsequent controlled studies have produced mixed results. Four studies have reported no increased rate of major congenital abnormalities among children born to women who use cannabis (Gibson et al, 1983; Hingson et al, 1982; Tennes et al, 1985; Zuckerman et al, 1989). One study has reported a five-fold increased risk of children with foetal alcohol like features being born to women who reported using cannabis (Hingson et al, 1982). The significance of this finding is uncertain because the same study also found no relationship between self-reported alcohol use and "foetal alcohol syndrome" features. This is doubly surprising because of other evidence on the adverse effects of alcohol, and because the epidemiological data indicates that cannabis and alcohol use are associated (Norton and Colliver, 1988). An additional study reported an increase in the crude rate of birth abnormalities among children born to women who reported using cannabis. This result was no longer statistically significant after adjustment for confounders (Linn et al, 1983), although the confidence interval around this adjusted risk (OR 1.36) only narrowly included the null value (95 per cent CI: 0.97, 1.91). The study by Zuckerman et al provides the most convincing failure to find an increased risk of birth defects among women who used cannabis during pregnancy. A large sample of women was obtained, among which there was a substantial prevalence of cannabis use that was verified by urinalysis. There was a low rate of birth abnormalities among the cannabis users, and no suggestion of an increase by comparison with the controls. On this finding, one might be tempted to attribute the small increased risk in the positive study (Linn et al, 1983) to recall bias, since the report of cannabis use during pregnancy was obtained retrospectively after birth, when women who had given birth to children with malformations may have been more likely to recall cannabis use than those who did not. However, given the uncertainty about the validity of self-reported cannabis use in many of the null studies, it would be unwise to exonerate cannabis as a cause of birth defects until larger, better controlled studies have been conducted. |
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Cancer
Kan den cancerhämmande drogen cannabis orsaka cancer? Ja, det kan nog diverse förbudsförespråkare inbilla befolkningen, men forskningen har inte kunnat hitta några starka bevis för påståendet.
| “ | Forskare har registrerat flera fall av sällsynta cancerformer hos barn till mödrar som rökt marijuana året före eller under graviditet. År 1989 rapporterades om en trefaldigt ökad risk för cancerformen akut icke-lymfatisk leukemi, 1992 en ökad risk för rhabdomyosarkom och 1993 en ökad risk för hjärn tumören astrocytom (Hall W. och Pacula R.L. 2003). I USA där dessa observationer har gjorts har man inte registrerat någon stadig ökning av dessa cancerformer i befolkningen under följande år. — Jan Ramström, Folkhälsoinstitutet - Skador av hasch och marijuana[46] |
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Franska INSERM dömer ut bevisen i sin rapport från 2001:
| “ | With regard to the development of cancer in the child exposed via maternal consumption, a case–control study reports an increased risk of acute non-lymphoblastic leukaemia in children exposed in the pre- or perinatal period. Paternal or maternal smoking, however, was not taken into account in this study, although it is a risk factor for leukaemia in the child. Two other case–control studies have explored the relationships between maternal cannabis consumption and cancer risks in the unborn child. One reports an increased risk of astrocytoma in children whose mothers were using cannabis at the time of conception or during pregnancy. Results, however, are at the limit of statistical significance. The other study shows an increased risk of rhabdomyosarcoma in children whose parents were cannabis users in the year preceding the birth of their child. This study shows a strong correlation between cannabis and cocaine use, which makes it impossible to determine the independent effects of these two psychoactive substances on the child's cancer risk. — INSERM[54] |
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EMCDDA menar också att sambanden är svaga:
| “ | Three studies exploring the risk of cancer in childhood have found evidence of a link with maternal cannabis use during pregnancy. The most notable of these studies found an association between maternal cannabis use and acute non-lymphoblastic leukaemia (ANLL). This case–control study was designed to assess the impact of the parents’ environmental exposure to petrochemicals, pesticides and radiation on childhood cancer, with maternal cannabis use recorded as one of the factors included in the analysis. The results showed that mothers of children with the cancers were 11 times more likely to have smoked cannabis than the comparison group. When the rate of cannabis use was adjusted among the control group to bring it up to the level of other studies of childhood cancer, the risk of cancer was still three times greater (Robinson et al., 1989). In the other two case–control studies, again investigating a range of factors that may have had an impact on childhood cancers, an increased risk of rhabdomyosarcoma and astrocytomas was found in children born to mothers who smoked cannabis during their pregnancy (Kuitjen et al., 1992; Grufferman et al., 1993). However, there is no evidence for an increase in incidence of these cancers over the period 1979–95, which would be expected if maternal cannabis use was a cause of these cancers (Hall and MacPhee, 2002). — EMCDDA, 2008[50] |
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Funktionsnedsättningar
Många av resultaten som presenteras bygger på Ottawa Prenatal Prospective Study (OPPS). Studien av Peter Fried av publicerats vid flera tillfällen genom åren, när deltagarna nått olika åldrar och med olika typer av utvärderingar. [55][56]. Man kommer fram till att effekten knappt är mätbar i ung ålder, men man kan se samband när barnen når skolåldern. Här nedan citeras resultatet vid en jämförelse med tobak under graviditeten. Problemen som noteras med cannabis kvarstod i en undersökning av ungdomar mellan 13-16 år[57]. Man bör också notera att i några deltester hade barnen till cannabisrökande mödrar högre resultat än övriga. I åldern 18-22 kunde man se att hjärnaktiviteten hade ökat i prefrontala cortex och premotoriska cortex. Man kunde även se en minskning i den vänstra delen av lillhjärnan när man utsatte personerna för utmanande tester [58].
| “ | In summary, the present findings indicate that, in the 9- to 12-year-old offspring, maternal cigarette use has markedly different associations with visuoperceptual functioning compared with maternal marihuana use. The data extend earlier reports in which prenatal cigarette exposure was associated with cognitive performance in a relatively ubiquitous fashion whereas the consequences of prenatal marihuana use were limited to cognitive tests that involved online integrative visual analysis and hypothesis testing. In the present report, maternal cigarette smoking appears to have its major impact upon fundamental aspects of visuoperceptual functioning compared with a lack of effect for prenatal marihuana use within this sphere. Rather, prenatal marihuana use is associated with the application of these fundamental abilities to problem-solving situations requiring integration, analysis and synthesis. The marihuana findings are consistent with the hypothesis that prenatal exposure to this drug impacts upon aspects of executive functioning. — Fried (1999)[59] |
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Thomas Lundqvist har skrivit en ganska omfattande artikel om OPPS där några slutsatser listas:
| “ | Marijuana resultaten kan summeras på följande sätt:
... Ett av de bestående resultaten i OPPS-studien (och i Pittsburgh-gruppen), var att prenatal marijuana påverkan inte hade något samband med ett försämrat allmänt IQ. ... Prenatal marijuana påverkan medför så långt som man idag kan skönja inga observerbara neurologiska långtidseffekter, däremot ser man en fördröjning av mognaden hos det fyra åriga barnet. Om barnet lever i en socialt och psykologiskt stödjande miljö, så har den fördröjning av mognadsutveckling försvunnit i fem eller sex års åldern. |
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Vidare till Jan Ramström:
| “ | En central plats inom denna forskning innehar Ottawa Prenatal Prospective Study (OPPS) som genomförts av en forskargrupp under ledning av Peter Fried. Bland annat genom sin långsiktighet är detta en unik undersökning av barn till mödrar som rökt marijuana under graviditeten. Mödrarna togs in i forskningsprogrammet under åren 1978–1983. Barnen undersöktes neurologiskt direkt efter födelsen och upprepade gånger under det första året och deras kognitiva och psykomotoriska funktioner har därefter testats årligen upp till 16 års ålder. Till en början fann man tecken på brister i den neurologiska utvecklingen, alternativt tecken på abstinens. Dessa symtom försvann under det första året, och vid undersökningarna av motorik, perception och motoriska funktioner vid ett, två och tre års ålder fann man inga brister som kunde hänföras till cannabisexponeringen under fosterlivet. Vid fyraårsundersökningen fann man däremot brister vad gällde minne och verbal förmåga. Dessa brister kvarstod inte vid fem– och sexårsundersökningarna. Vid sexårsundersökningen fann man dock brister i förmågan att bibehålla uppmärksamhet. Vid undersökningarna mellan sex och nio års ålder fann man flera uttryck för brister i de kognitiva funk tionerna. Föräldrarna till de marijuanaexponerade rapporterade också i högre utsträckning beteende störningar hos barnen. Vid nio-tolvårsundersökningarna fann man måttliga funktionsinskränkningar av en bestämd typ. Barnen hade sänkt förmåga när det gällde minne i anslutning till visuella stimuli, analysförmåga och inte grations förmåga. Man fann också uppmärksamhetsstörningar. Samma mönster återfanns vid mät ningar i åldern 13–16 år (Fried, et al., 2003). Det kan nämnas att störningarna hos barn vars mödrar rökt cannabis under graviditeten skiljde sig från de hos barn vars mödrar enbart rökt vanliga cigaretter. Dessa barn påverkades vad gällde övergripande intelligens och vissa hörselrelaterade funktioner.
Sammanfattningsvis fann man – förutom övergående milda neurologiska störningar efter födelsen – lättare störningar av kognitiva funktioner som märktes först vid fyra års ålder och senare försvann. Andra störningar av kognitiva funktioner jämte beteendeproblem visade sig under de första skolåren och har kunnat följas i tonåren. Fried (1995; 2003) har en hypotes om varför störningarna märks först efter några år. Den står i samklang med de kognitiva skador som drabbar vuxna efter långvarig cannabisrökning. De skador som uppstår under fosterlivet antas få betydelse först då barnet behöver fungera på en högre nivå i fråga om så kallade exekutiva funktioner (integrerande kognitiva funktioner som bland annat är viktiga för problemlösning och planering). Det är bland annat sådana kognitiva störningar som också drabbar vuxna (Leavitt, et al., 1994). De flesta undersökningar av cannabispåverkan under graviditet pågår inte längre än till ettårsåldern, varför Fried och hans medarbetares resultat endast i mycket begränsad utsträckning har kunnat stödjas respektive ifrågasättas på vetenskaplig grund. Day et al (1993) fann samband mellan marijuanarökning under graviditeten och lägre resultat på intelligenstestning vid tre års ålder (men inte tidigare), ett fynd som stödjer Frieds resultat. Ett samband mellan marijuanarökning under graviditet och sömnstörningar i treårsåldern som påvisats i Dahls studie (1995) går i samma riktning. Peter Fried (1995) varnar för en underskattning av riskerna för fostret vid cannabisexponering under graviditeten. Han understryker att undersökningen avser effekterna av marijuanarökning i slutet på 1970-talet och påminner om att den marijuana som används i dag innehåller betydligt högre koncentration av THC. Numera finns dock ytterligare en långsiktig undersökning där barnen är 5–6 år yngre. Goldschmidt et al. (2002) studerade en grupp på drygt 600 gravida kvinnor där knappt hälften rökte olika mängder marijuana under graviditeten. Man gjorde noggranna undersökningar av hemsituationen med mera under graviditeten och efter förlossningen i avsikt att renodla eventuell cannabispåverkan. Man lade huvudvikten – under de första åren – vid rapporter från föräldrar och senare lärare. Vid sex års ålder fann man ett samband mellan marijuanaexponering och lärarnas rapporter om störande beteende (delinquent behavior problems). Vid tio års ålder gjordes en mer omfattande bedömning som inkluderade föräldra- och lärarintervju och standardiserade frågeformulär. Man fann en tydlig koppling mellan exponering och delinquency, ungefär regelöverträdande beteende. Vidare fann man att dessa beteendestörningar medierades av påtaglig hyper aktivitet, impulsivitet och brister i uppmärksamhet, förhållningssätt som hade ett samband med graden av marijuanaexponering. När man jämför de två långsiktiga studierna ser man flera liknande tendenser, bland annat att testutslag respektive beteendestörningar kommer sent, som ett uttryck för att det är då skadade funktioner utvecklas och kommer till användning. Andra likheter är föräldrars respektive lärares rapporter om stört/oroligt beteende som kommer vid ungefär samma ålder. Fried har mer inriktat sig på att mäta kognitiva funktioner och Goldschmidt registrerar beteende. I en annan kohort har man nu prövat om den ovan nämnda intellektuella nivåsänkningen hos treåringar också skulle visa sig hos sexåringarna inför skolstarten. Svaret blev att cannabisrökning under graviditet kan sänka den intellektuella nivån hos det sexåriga barnet (L. Goldschmidt et al 2008). |
” |
Hall sammanfattar forskningen fram till 2001, bland annat nämns en ännu större studie där man inte kunnat replikera Frieds resultat:
| “ | The most extensive research on the effects of cannabis use during pregnancy on the post-natal development of the child comes from the Ontario Prospective Prenatal Study (OPPS). This study assessed developmental and behavioural abnormalities in children born to women who reported using cannabis during pregnancy (31–39). A sample of 698 mothers were asked about their drug use during pregnancy and their children were measured on the Brazelton scales after birth and neurologically assessed at one month. In subsequent studies, these children were assessed using standardised scales at six and twelve months and throughout their childhood and into their adolescence (31).
The initial OPPS studies reported a developmental delay shortly after birth in the infants’ visual system, and an increased rate of tremors and startle among the children born to cannabis users (31). The effects found at birth faded by one month, and there were no differences in performance on standardised tests of ability at six and twelve months. Small effects were again reported at 36 and 48 month follow ups (40) but these were not found at 60 and 72 months (41). These results are suggestive of a transient developmental impairment occurring among children who had experienced a shorter gestation and prematurity. It seems unlikely that the tests used in later follow-ups were insensitive to the effects of prenatal cannabis exposure because they showed adverse effects of tobacco smoking during pregnancy on behavioural development at 60 and 72 months (40, 41). The results of studies that have attempted to replicate the OPPS findings have been mixed. Tennes et al (23) conducted a prospective study of the relationship between cannabis use during pregnancy and postnatal development in 756 women, a third of whom reported using cannabis during their pregnancy. The children were assessed shortly after birth using the same measures as Fried (20) and a subset were assessed at one year of age. There were no differences in behavioural development after birth between the children of women who did and did not use cannabis and there were no differences at one year. More recently, Day et al (42), have followed up children at age three born to 655 women who were asked about their substance use during pregnancy. They found a relationship between the mothers’ cannabis use during pregnancy and the children’s performances on memory and verbal scales of the Stanford-Binet Intelligence Scale at age three. A later follow up at age six did replicate the OPPS findings of increased impulsivity and impaired attention among children whose mothers had smoked cannabis during their pregnancy (43). Fried and Smith (31) concluded after reviewing the literature that the effects of ‘prenatal exposure to marihuana are subtle’ and ‘considerably moderated by other risk factors’. There were ‘limited (if any) effects upon foetal growth and central nervous system functioning’ and little evidence of effects on growth and behaviour during the toddler stage. They argued that there was suggestive evidence for subtle effects after the age of three in impulsivity, attention and problem solving, the significance of which needed to be clarified by further research. A more sceptical view was expressed in a recent meta-analytic review of the effects on foetal development of maternal use of cocaine, a drug with a much greater reputation for foetal toxicity than cannabis (44). Frank et al concluded that, after controlling for exposure to tobacco and alcohol, there were no effects of prenatal cocaine use on physical of behavioural development to age six. |
” |
Franska INSERM tycker att bevisningen är svag
| “ | Behavioural anomalies have been observed in some studies in neonates of mothers who are regular cannabis users: increased trembling, decreased visual response to light stimuli, reduction in the strength of crying, deterioration in sleep, and increased impulsivity. These signs generally regress on the 30th day. One study, however, reports the persistence of a decreased visual response in children 4 years of age exposed in the prenatal period. This anomaly disappears at 5 or 6 years of age. In the same study, no reduction in mental and motor performance or language ability has been found in children 1 and 2 years of age. One recent prospective study concludes that there is a significant relationship between certain behavioural disorders at the age of 10 years and prenatal exposure to cannabis. However, the postnatal environment could play an important role in the persistence of these behavioural anomalies.
It must be noted that most published epidemiological studies are characterised by little or no information on the extent, duration and weekly exposure time of consumption. They tend to contain no analytical confirmation, and by selecting subjects from underprivileged socioeconomic backgrounds, they provide no information on the postnatal environmental conditions that could influence any assessment of effects. |
” |
EMCDDA refererar till senare studier där man kan se nedsättningar när barnen når skolåldern. Men trots att man tar hänsyn till bl.a socioekonomiska faktorer som kan påverka resultatet så tar man inte hänsyn till föräldrarnas delaktighet i uppfostran och skolgång.
| “ | There are two major ongoing longitudinal studies examining prenatal exposure and subsequent effects on growth, cognitive development and behaviour. The first is the Ottawa Prospective Prenatal Study (OPPS), under way since 1978. The sample in this study consists of low-risk, white and predominantly middle-class families. The second study, the Maternal Health Practices and Child Development Study (MHPCD), began in 1982. The study sample is high-risk, with low socioeconomic status and just over half are African American (Goldschmidt et al., 2000).
The OPPS found that there was a developmental delay after birth in the infant’s visual system with an increased rate of tremors and startle among the children of cannabis users. These effects had disappeared after 1 month and there were no detectable effects on standardised ability tests at 6 months and 12 months (Fried and Smith, 2001). The cohort has now been followed up to age 13–16 years. Effects were found on memory at age 4, attention at age 6 and visual integration and attention and visual-related aspects of executive function in 9- to 12-year-olds. There was no difference between children who were and were not prenatally exposed to cannabis on global IQ scores but there were differences in tasks that required visual memory, analysis and integration at age 13–16 (Fried et al., 2003). A recent study from the Pittsburgh MHPCD examined the effects of prenatal cannabis and alcohol exposure on academic achievement at age 10. In contrast to the OPPS, which found no effects of prenatal exposure to cannabis on school performance, use of cannabis in the first trimester was associated with poorer performance on reading and spelling tests and a lower performance evaluation by the children’s teachers. Analysis suggested these effects were mediated by the effect of first-trimester use of cannabis on the children’s anxiety and depression symptoms. Cannabis use in the second trimester was significantly associated with underachievement in school performance. While a range of factors, including socioeconomic, home environment and maternal prenatal and current drug use, were taken into account in the study, other important factors such as motivation and parental involvement in the child’s education did not feature in the statistical analysis (Goldschmidt et al., 2004). |
” |
Slutligen en studie från Jamaica visar att nyfödda barn till cannabisrökande mödrar är mer alerta, har bättre motorik och är mindre irriterade:
| “ | Participants. Twenty-four Jamaican neonates exposed to marijuana prenatally and 20 nonexposed neonates.
Measurements and main results. Exposed and nonexposed neonates were compared at 3 days and 1 month old, using the Brazelton Neonatal Assessment Scale, including supplementary items to capture possible subtle effects. There were no significant differences between exposed and nonexposed neonates on day 3. At 1 month, the exposed neonates showed better physiological stability and required less examiner facilitation to reach organized states. The neonates of heavy-marijuana-using mothers had better scores on autonomic stability, quality of alertness, irritability, and self-regulation and were judged to be more rewarding for caregivers. Conclusions. The absence of any differences between the exposed on nonexposed groups in the early neonatal period suggest that the better scores of exposed neonates at 1 month are traceable to the cultural positioning and social and economic characteristics of mothers using marijuana that select for the use of marijuana but also promote neonatal development. ... Although no positive or negative neurobehavioral effects of prenatal exposure were found at 3 days of life using the Brazelton examination, there were significant differences between the exposed and nonexposed neonates at the end of the first month. Comparing the two groups, the neonates of mothers who used marijuana showed better physiological stability at 1 month and required less examiner facilitation to reach an organized state and become available for social stimulation. The results of the comparison of neonates of the heavy-marijuana-using mothers and those of the nonusing mothers were even more striking. The heavily exposed neonates were more socially responsive and were more autonomically stable at 30 days than their matched counterparts. The quality of their alertness was higher; their motor and autonomic systems were more robust; they were less irritable; they were less likely to demonstrate any imbalance of tone; they needed less examiner facilitation to become organized; they had better self-regulation; and were judged to be more rewarding for caregivers than the neonates of nonusing mothers at 1 month of age. |
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Källor
- ↑ Haschboken (Barbro Holmberg, Folkhälsoinstitutet, 1994)
- ↑ Drugnews - Cannabis
- ↑ Association Between Marijuana Use and Sexual Frequency in the United States: A Population-Based Study (Sun, 2017)
- ↑ Baked Sex: the Exploration of Sex-Related Drug Expectancies of Marijuana Users (Currin, 2017)
- ↑ Neuroscience News 2017-10-27: Researchers Link Regular Marijuana Use to More Sex
- ↑ Reduction of the fertilizing capacity of sea urchin sperm by cannabinoids derived from marihuana. I. Inhibition of the acrosome reaction induced by egg jelly. (Schuel, 1991)
- ↑ Evidence for a cannabinoid receptor in sea urchin sperm and its role in blockade of the acrosome reaction. (Chang, 1993)
- ↑ New Scientist 2000-12-12: Cannabis slows sperm swimming in the test tube, potentially explaining low fertility among heavy marijuana users
- ↑ 9,0 9,1 9,2 9,3 The health and psychological effects of cannabis use (Hall, 2001)
- ↑ University at Buffalo: Sperm from Marijuana Smokers Move Too Fast Too Early, Impairing Fertility, UB Research Shows
- ↑ Evidence that anandamide-signaling regulates human sperm functions required for fertilization (Schuel & Burkman, 2002)
- ↑ A tale of two cells: endocannabinoid-signaling regulates functions of neurons and sperm (Schuel & Burkman, 2005)
- ↑ Marijuana smoking and markers of testicular function among men from a fertility centre (Nassan, 2019)
- ↑ European Society of Human Reproduction and Embryology 2019-02-05: Unexpected results suggest a few joints may not harm men's sperm
- ↑ LiveScience 2019-02-06: Smoking Marijuana Linked to Better Sperm Counts in Surprising Study
- ↑ Effects of delta-9-tetrahydrocannabinol, the primary psychoactive cannabinoid in marijuana, on human sperm function in vitro (Whan, 2006)
- ↑ British Fertility Society: How cannabis can affect sperm to reduce fertility
- ↑ Effects of chronic bhang (cannabis) administration on the reproductive system of male mice. (Banerjee, 2011)
- ↑ Association Between Use of Marijuana and Male Reproductive Hormones and Semen Quality: A Study Among 1,215 Healthy Young Men (Gundersen, 2015)
- ↑ The CB2 cannabinoid receptor regulates human sperm cell motility (Agirregoitia, 2010)
- ↑ Type 2 cannabinoid receptor contributes to the physiological regulation of spermatogenesis (Di Giacomo, 2016)
- ↑ Caffeine Intake and Semen Quality in a Population of 2,554 Young Danish Men (Jensen, 2010)
- ↑ The effects of male age on sperm DNA damage in healthy non-smokers (Schmid, 2006)
- ↑ New Scientist: Cannabis-based boost for smokers suffering sperm
- ↑ Can Cannabinoid Compounds Reverse the Effects of Nicotine on Human Sperm Fertilizing Functions? av Tiffany Weathers, M.D.
- ↑ Dietary patterns and semen quality in young men (Gaskins, 2012)
- ↑ Science Daily: Soy Foods Are Associated With Lower Sperm Concentrations
- ↑ Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic (Chavarro, 2008)
- ↑ BBC: Soya 'link' to male infertility
- ↑ Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence (Messina, 2010)
- ↑ Decreased sperm concentration and motility in a subpopulation of vegetarian males at a designated blue zone geographic region (Orzylowska, 2014)
- ↑ Processed Meat Intake Is Unfavorably and Fish Intake Favorably Associated with Semen Quality Indicators among Men Attending a Fertility Clinic Afeiche, 2014
- ↑ Meat intake and reproductive parameters among young men (Afeiche, 2014)
- ↑ Dairy food intake in relation to semen quality and reproductive hormone levels among physically active young men (Afeiche, 2013)
- ↑ Independent 2010-04-26: Out for the count: Why levels of sperm in men are falling
- ↑ Wet heat exposure: a potentially reversible cause of low semen quality in infertile men. (Shefi, 2007)
- ↑ Physical activity and semen quality among men attending an infertility clinic (Wise, 2010)
- ↑ Science Daily: Caffeine Consumption Linked to Female Infertility, Study Suggests
- ↑ A prospective study of the effects of female and male caffeine consumption on the reproductive endpoints of IVF and gamete intra-Fallopian transfer (Klonoff-Cohen, 2002)
- ↑ Karolinska Institutet - Utbildning - Droger
- ↑ Cannabismissbruk. Trestad – Stockholm 2012-04-27
- ↑ CAN: Drogfakta. Cannabis - hasch och marijuana
- ↑ Behandling av alkohol- och narkotikaproblem (SBU. Statens beredning för medicinsk utvärdering, 2001)
- ↑ Use of Marijuana During Pregnancy By Lynn Zimmer and John P. Morgan
- ↑ Cannabis och farlighet (Lundqvist, 2003)
- ↑ 46,0 46,1 46,2 46,3 Folkhälsoinstitutet - Skador av hasch och marijuana
- ↑ 47,0 47,1 The health and psychological consequences of cannabis use - chapter 6 (Hall, Solowij & Lemon, 1994)
- ↑ Maternal cannabis use and birth weight: a meta-analysis (English et al, 1997)
- ↑ Cannabis and pregnancy (Balle, 1999)
- ↑ 50,0 50,1 50,2 EMCDDA: A cannabis reader: global issues and local experiences Perspectives on cannabis controversies, treatment and regulation in Europe (2008)
- ↑ Characteristics of pregnant illicit drug users and associations between cannabis use and perinatal outcome in a population-based study
- ↑ Caffeine intake and pregnancy outcomes: a meta-analytic review (Santos, 1998)
- ↑ Maternal caffeine intake during pregnancy is associated with birth weight but not with gestational length: results from a large prospective observational cohort study (Sengpiel, 2013)
- ↑ 54,0 54,1 INSERM Collective Expert Reports: Cannabis: Effects of consumption on health (Institut national de la santé et de la recherche médicale, 2001)
- ↑ Prenatal exposure to marihuana and tobacco during infancy, early and middle childhood: effects and an attempt at synthesis. (Fried, 1995)
- ↑ Conceptual issues in behavioral teratology and their application in determining long-term sequelae of prenatal marihuana exposure. (Fried, 2002)
- ↑ Differential effects on cognitive functioning in 13- to 16-year-olds prenatally exposed to cigarettes and marihuana. (Fried, 2003)
- ↑ Effects of prenatal marijuana on response inhibition: an fMRI study of young adults (Smith, 2004)
- ↑ Visuoperceptual functioning differs in 9- to 12-year olds prenatally exposed to cigarettes and marihuana (Fried, 1999)
- ↑ Från vaggan till tonåren (Lundqvist, 2003)
- ↑ Prenatal Marijuana Exposure and Neonatal Outcomes in Jamaica: An Ethnographic Study (Dreher, 1994)
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