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Cannabis

Trials of mostly oral cannabis medicines found small gains in chronic pain and sleep against placebo, and no clear gain in appetite. In observational studies of users, sperm findings are mixed, with poorer sperm shape in one pooled analysis and no link to time to pregnancy. Use is linked to dependence, psychosis, lower birth weight and car crashes.

Checked 2026-11-13
Status
A daily life factor, not a product. Marijuana is a Schedule I controlled substance under US federal law [1]. Dronabinol, a synthetic THC, is in Schedule III when it is in an FDA-approved product [2].
Also called
marijuana, marihuana, weed, pot, THC, delta-9-THC, smoking weed, edibles, vaping cannabis, recreational cannabis, medical cannabis, medical marijuana, hashish, cannabis use, nabiximols, Sativex, dronabinol, nabilone
Studied for
sleep, insomnia, chronic pain, nerve pain, anxiety, appetite, weight gain

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help2

Reported risks8

What it was studied for, and what was found

Shown to help2

Strong

Chronic pain

Shown to slightly reduce chronic pain against placebo, mostly with oral cannabis medicines. About 1 in 24 more people reached a 30% drop in pain.

Compared with placebo in 29 of 32 trials, and other non-cannabis controls [3]; placebo [4][5]

The numbers and sources
Effect
Across 32 trials of 5,174 adults, non-inhaled medical cannabis raised the share of people reaching a meaningful pain reduction of 1 cm on a 10 cm scale by 10 percentage points (95% CI 5 to 15), with pain 0.50 cm lower (95% CI -0.75 to -0.25, moderate certainty). Physical functioning improved very slightly, and emotional, role and social functioning did not change [3]. Across 47 RCTs in chronic noncancer pain, 29.0% on cannabinoids and 25.9% on placebo reached a 30% pain reduction, a number needed to treat of 24 (95% CI 15 to 61). A 50% reduction (18.2% against 14.4%) did not differ, and pain intensity fell by the equivalent of 3 mm on a 100 mm scale [4]. Across 8 trials, 37% on cannabinoids and 31% on placebo reported pain reduction (OR 1.41, 95% CI 0.99 to 2.00) [5].
Population
Adults with chronic noncancer or cancer pain, followed 1 to 5.5 months [3]; people with neuropathic pain, fibromyalgia, multiple sclerosis pain and other chronic noncancer pain [4]; trial participants with chronic pain [5].
Sources
[3], [4], [5]
Caveats
Almost all trials tested oral or mouth-spray medicines such as nabiximols, dronabinol, nabilone and oral extracts, not smoked cannabis [3]. Only 4 of 79 trials in one review were at low risk of bias [5]. Results for CBD alone are on the CBD page.
Strong

Sleep

Shown to slightly improve sleep quality and sleep disturbance against placebo in people with chronic pain, in two reviews of mostly oral cannabis medicines.

Compared with placebo and other non-cannabis controls [6][3]; placebo [4]

The numbers and sources
Effect
Across 39 trials of 5,100 patients, 8% more people with chronic pain reached a meaningful improvement in sleep quality (95% CI 3 to 12, moderate certainty), and 19% more people with chronic noncancer pain reached a meaningful improvement in sleep disturbance (95% CI 11 to 28). In cancer pain the improvement was very small (WMD -0.19 cm, 95% CI -0.36 to -0.03) [6]. Across chronic pain trials, 6% more reached a meaningful gain in sleep quality (95% CI 2 to 9), with scores 0.35 cm better on a 10 cm scale (95% CI -0.55 to -0.14, high certainty) [3]. A third review found low-quality evidence of improved sleep [4].
Population
5,100 patients, 33 of 39 trials in people with chronic cancer or noncancer pain, median follow-up 35 days [6]; adults with chronic pain [3][4].
Sources
[6], [3], [4]
Caveats
38 of 39 trials gave oral cannabinoids and one gave inhaled cannabis, and few enrolled people with sleep problems alone [6]. The two main reviews come from one research group and share trials.

Mixed results1

Moderate

Anxiety

Mixed results: THC medicines slightly eased anxiety symptoms in people with pain or multiple sclerosis, at very low certainty, and evidence for anxiety disorders was scarce.

Compared with placebo [7]

The numbers and sources
Effect
In 7 studies of 252 people with other medical conditions, mainly chronic noncancer pain and multiple sclerosis, pharmaceutical THC with or without CBD improved anxiety symptoms (SMD -0.25, 95% CI -0.49 to -0.01, very low GRADE). Across 17 RCTs for anxiety, THC did not significantly change other primary outcomes, and few trials tested medicinal cannabis [7].
Population
605 participants in 17 randomized trials for anxiety, within 83 studies of cannabinoids for mental disorders [7].
Sources
[7]
Caveats
Very low certainty, small trials, and anxiety was a secondary symptom in people treated for other conditions [7].

Not shown to help1

Moderate

Appetite and weight

Not shown to raise appetite or weight in people with cancer or wasting, in pooled trials of cannabis medicines.

Compared with placebo or other active treatments [8]; placebo or megestrol acetate [9]; placebo [10]

The numbers and sources
Effect
Across 5 trials of 934 people with cachexia, appetite change did not differ significantly and leaned toward the control group (effect size -1.79, 95% CI -3.77 to 0.19), and weight and quality of life did not differ [8]. Across 5 trials in people with cancer, one found dronabinol improved taste of food and premeal appetite against placebo, and the others did not show efficacy [9]. Across 3 trials of 592 people with cancer cachexia, appetite did not differ significantly (MD 0.27, 95% CI -0.51 to 1.04), and quality of life was lower with cannabinoids (MD -12.39, 95% CI -24.21 to -0.57) [10].
Population
People with cachexia from chronic disease [8]; people with cancer [9][10].
Sources
[8], [9], [10]
Caveats
Few trials with varied products and measures. Evidence quality was low [8]. No pooled trial data were located for appetite in healthy people.

Amounts studied

Trials gave medical cannabis or cannabinoids by mouth, as a mouth spray or on the skin, mostly nabiximols, dronabinol, nabilone or oral extracts, for 1 to 5.5 months [3][6]. Observational studies grouped people by how often they used: more than once a week in the past 3 months [11], more than one joint a week [12], daily use in the past 12 months [13], or daily use of high-potency cannabis with 10% THC or more [14]. CBD alone is covered on its own page.

Risks

Reported risks7

ModerateVery common

Dependence (cannabis use disorder)

Linked to cannabis use disorder in about 22% of people who use cannabis, and dependence in a third of young people using weekly or daily.

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
Among people who had used cannabis, 22% (95% CI 18% to 26%) had cannabis use disorder, 13% cannabis abuse and 13% cannabis dependence. In cohort studies, the risk of dependence rose to 33% (95% CI 22% to 44%) among young people who used weekly or daily [20].
Population
People in the general population who had used cannabis, in 21 cross-sectional and longitudinal studies [20].
Sources
[20]
Caveats
Definitions followed DSM or ICD criteria but varied between studies, and few cohorts measured disorder in regular users [20].
StrongVery common

Side effects in trials

Shown to raise side effects against placebo, especially dizziness, drowsiness and nausea, with one extra person affected for every 6 treated.

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
In chronic pain trials, 81.2% on cannabinoids and 66.2% on placebo had an adverse event, a number needed to harm of 6 (95% CI 5 to 8) [4]. Dizziness rose by 9 percentage points in trials under 3 months and 28 points in longer trials, with smaller rises in drowsiness (5), nausea (5), vomiting (3), impaired attention (3) and transient cognitive impairment (2) [3]. Sleep trials found dizziness 29 points higher in trials of 3 months or more, and somnolence, dry mouth, fatigue and nausea 6 to 10 points higher [6]. In trials for mental disorders, more people had adverse events (OR 1.99, 95% CI 1.20 to 3.29) and withdrew because of them (OR 2.78, 95% CI 1.59 to 4.86) [7]. Serious adverse events were also more frequent [5].
Population
Adults in randomized trials of cannabis medicines [4][3][6][7][5].
Sources
[4], [3], [6], [7], [5]
Caveats
These are oral cannabis medicines at trial doses. Side effects of smoked or high-potency products were not measured in these trials.
ModerateHow often is not known

Psychosis

Linked to about four times the odds of psychosis in the heaviest users, and nearly five times with daily high-potency cannabis, in pooled and case-control studies.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Across 10 studies of 66,816 people, the heaviest users had higher odds of schizophrenia and other psychotic outcomes than non-users (OR 3.90, 95% CI 2.84 to 5.34), with a dose-response pattern [21]. Across 11 sites with 901 first-episode patients and 1,237 controls, daily use carried higher odds of psychotic disorder than never using (OR 3.2, 95% CI 2.2 to 4.1), and daily use of cannabis with 10% THC or more carried an OR of 4.8 (95% CI 2.5 to 6.3) [14].
Population
People in 10 studies that recorded cannabis use before psychosis began [21]; adults aged 18 to 64 in Europe and Brazil [14].
Sources
[21], [14]
Caveats
Observational. The authors note a causal link cannot be firmly established [21], and people vulnerable to psychosis may be drawn to cannabis.
StrongStudied in pregnancyHow often is not known

Use in pregnancy

Linked to lower birth weight, more preterm and small-for-age babies and more newborn intensive care admissions when used in pregnancy, in two pooled analyses.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Across 24 studies, mothers who used cannabis had higher odds of anemia (OR 1.36, 95% CI 1.10 to 1.69), and their babies had higher odds of low birth weight (OR 1.77, 95% CI 1.04 to 3.01), weighed 109 g less and more often needed neonatal intensive care (OR 2.02, 95% CI 1.27 to 3.21) than babies of non-users [22]. Across 16 studies of 59,138 patients, exposure was linked to birth weight under 2,500 g (RR 2.06, 95% CI 1.25 to 3.42), small size for gestational age (RR 1.61), preterm delivery (RR 1.28, 95% CI 1.16 to 1.42), neonatal intensive care (RR 1.38) and 112 g lower birth weight [23].
Population
Pregnant women and their newborns in case-control, cross-sectional and cohort studies [22][23].
Sources
[22], [23]
Caveats
Observational. Women who use cannabis in pregnancy more often smoke tobacco and differ in other ways, which studies adjusted for unevenly.
StrongHow often is not known

Car crashes after use

Linked to higher crash risk when driving after cannabis, about 1.4 to 1.9 times the odds of unimpaired driving in two pooled analyses.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Across 9 observational studies, driving under the influence of cannabis was linked to higher odds of a crash than unimpaired driving (OR 1.92, 95% CI 1.35 to 2.73), and to fatal crashes (OR 2.10, 95% CI 1.31 to 3.36) [24]. A revised analysis of 28 estimates from 21 studies found a smaller increase (OR 1.36, 95% CI 1.15 to 1.61), and estimates fell further in better-adjusted studies [25].
Population
Drivers in case-control and culpability studies from 5 countries [24] and 13 countries [25].
Sources
[24], [25]
Caveats
Observational. Estimates were higher in studies that did not control for alcohol [25].
StrongStudied in menHow often is not known

Testicular cancer

Linked to higher odds of testicular germ cell cancer with current or long-term use, especially nonseminoma, in two pooled analyses of few studies.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Across 3 US case-control studies, weekly or more frequent use was linked to 2.59 times the odds of nonseminoma (95% CI 1.60 to 4.19), with inconclusive results for seminoma [26]. Across 5 studies, current use (OR 1.62, 95% CI 1.13 to 2.31) and use for 10 years or more (OR 1.68, 95% CI 1.19 to 2.36) were linked to testicular germ cell tumors [27].
Population
Men in 3 case-control studies [26]; men in 3 case-control and 2 cohort studies [27].
Sources
[26], [27]
Caveats
Observational, few studies, much of the data collected in the 1990s in the US [26]. Users may differ from non-users in other exposures, which the studies adjusted for in different ways [27]. Testicular cancer is uncommon, so a raised odds ratio is a small absolute change.
LimitedHow often is not known

Heart attack and stroke

Linked to higher odds of heart attack and stroke with daily use in one large US survey, including in people who never smoked tobacco.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
In 434,104 US adults, daily cannabis use was linked to higher odds of myocardial infarction (aOR 1.25, 95% CI 1.07 to 1.46) and stroke (aOR 1.42, 95% CI 1.20 to 1.68) than no use. Coronary heart disease did not differ significantly (aOR 1.16, 95% CI 0.98 to 1.38). In never tobacco smokers, daily use was linked to myocardial infarction (aOR 1.49) and stroke (aOR 2.16) [28].
Population
434,104 adults aged 18 to 74 in the Behavioral Risk Factor Surveillance Survey, 2016 to 2020 [28].
Sources
[28]
Caveats
Cross-sectional and self-reported, so it cannot show which came first, and the authors adjusted for tobacco use but other differences between users and non-users may remain [28].

Mixed results1

ModerateStudied in menVery common

Sperm count and quality

Mixed results: pooled studies linked cannabis use to slightly poorer sperm shape but not to count or motility, while single large studies found lower or higher counts in users.

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
Across 9 studies of 4,014 men, 44.9% of cannabis users and 24.5% of non-users had an impaired semen measure, a difference that was not significant (RR 1.159, 95% CI 0.840 to 1.599). FSH was slightly lower in users (SMD -0.142) [15]. Across 18 studies of 5,766 men, users had lower normal sperm morphology than non-users (MD -1.02, 95% CI -1.93 to -0.10), and sperm concentration, total count, semen volume and motility did not differ [12]. In 1,215 young Danish men, use more than once a week was linked to 28% lower sperm concentration (95% CI -48 to -1) and 29% lower total count than no use, and 52% lower concentration when combined with other drugs [11]. In 662 men at a US fertility center, men who had ever smoked marijuana had higher sperm concentration than men who never had (62.7 against 45.4 million/mL) [16].
Population
Men in population-based and clinic studies [15][12]; 1,215 Danish men aged 18 to 28 at military fitness exams [11]; 662 subfertile US men [16].
Sources
[15], [12], [11], [16]
Caveats
Observational, with use self-reported. Cannabis users differ from non-users in tobacco, alcohol and other drug use, which studies adjusted for unevenly. Semen measures are not pregnancies.

Checked, no increase found2

Limited

Time to pregnancy and live birth when the man uses cannabis

Not linked to longer time to pregnancy when men used cannabis, in two population studies. A fertility clinic study unexpectedly linked male use to more live births.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
In a US national survey of 758 men trying to conceive, time to pregnancy did not differ between daily users and never users (time ratio 1.08, 95% CI 0.79 to 1.47) [13]. In 1,125 North American couples, fecundability did not differ when the man used cannabis less than weekly (FR 0.87, 95% CI 0.66 to 1.15) or weekly or more (FR 1.24, 95% CI 0.90 to 1.70) against no use [17]. In couples having IVF or related treatment, those in which the man currently smoked marijuana had a higher adjusted live birth rate than those in which he had never or only previously smoked (48% against 29%, p = 0.04) [18].
Population
758 men and 1,076 women trying to conceive in the US National Survey of Family Growth [13]; 4,194 women and 1,125 male partners in a preconception cohort [17]; 421 women and their partners in 730 assisted reproduction cycles, 23 men current smokers [18].
Sources
[13], [17], [18]
Caveats
Observational, with self-reported use, and men who use cannabis differ from non-users in tobacco, alcohol and other habits. The clinic finding rests on few exposed men and may be chance [18]. The survey measured time to pregnancy retrospectively [13].
StrongStudied in men

Lower testosterone

Not linked to lower testosterone in men in two pooled analyses and a national US survey. Some studies found slightly higher testosterone in recent users.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Across studies of 4,787 men with hormone data, testosterone did not differ between users and non-users (SMD -0.139, 95% CI -0.413 to 0.134) [15]. A pooled analysis of 21,066 men found no difference in testosterone, FSH or LH, and higher SHBG in users (MD 3.90, 95% CI 1.67 to 6.13) [12]. In 1,577 US men, testosterone was 3.69 ng/mL in ever users and 3.70 ng/mL in never users, and was higher with more recent use [19]. Danish users had higher testosterone than non-users [11].
Population
Men in pooled observational studies [15][12]; 1,577 men in NHANES 2011 to 2012 [19]; 1,215 young Danish men [11].
Sources
[15], [12], [19], [11]
Caveats
Cross-sectional, with one blood sample per man and self-reported use, so differences in tobacco use, weight and other habits may confound the comparison. Timing of the last use affects levels [19].

Claims tested and not found

  1. That cannabis lowers testosterone in men. Testosterone did not differ between users and non-users in pooled studies (SMD -0.139, 95% CI -0.413 to 0.134) [15] or in a US national survey [19].
  2. That a man's cannabis use delays pregnancy. Time to pregnancy did not differ between men who used daily and men who never used (time ratio 1.08, 95% CI 0.79 to 1.47) [13].
  3. That cannabis medicines raise appetite and weight in people with wasting. Across 5 trials, appetite and weight did not differ from control [8].

Related

CBD

Sources

  1. Electronic Code of Federal Regulations. 21 CFR 1308.11, Schedule I. eCFR. 2026. https://www.ecfr.gov/current/title-21/chapter-II/part-1308/section-1308.11
  2. Electronic Code of Federal Regulations. 21 CFR 1308.13, Schedule III. eCFR. 2026. https://www.ecfr.gov/current/title-21/chapter-II/part-1308/section-1308.13
  3. Wang L, Hong PJ, May C, et al. Medical cannabis or cannabinoids for chronic non-cancer and cancer related pain: a systematic review and meta-analysis of randomised clinical trials. BMJ. 2021. https://doi.org/10.1136/bmj.n1034
  4. Stockings E, Campbell G, Hall WD, et al. Cannabis and cannabinoids for the treatment of people with chronic noncancer pain conditions: a systematic review and meta-analysis of controlled and observational studies. Pain. 2018. https://doi.org/10.1097/j.pain.0000000000001293
  5. Whiting PF, Wolff RF, Deshpande S, et al. Cannabinoids for Medical Use: A Systematic Review and Meta-analysis. JAMA. 2015. https://doi.org/10.1001/jama.2015.6358
  6. AminiLari M, Wang L, Neumark S, et al. Medical cannabis and cannabinoids for impaired sleep: a systematic review and meta-analysis of randomized clinical trials. Sleep. 2022. https://doi.org/10.1093/sleep/zsab234
  7. Black N, Stockings E, Campbell G, et al. Cannabinoids for the treatment of mental disorders and symptoms of mental disorders: a systematic review and meta-analysis. The Lancet Psychiatry. 2019. https://doi.org/10.1016/s2215-0366(19)30401-8
  8. Hammond S, Erridge S, Mangal N, et al. The Effect of Cannabis-Based Medicine in the Treatment of Cachexia: A Systematic Review and Meta-Analysis. Cannabis and Cannabinoid Research. 2021. https://doi.org/10.1089/can.2021.0048
  9. Razmovski-Naumovski V, Luckett T, Amgarth-Duff I, Agar MR. Efficacy of medicinal cannabis for appetite-related symptoms in people with cancer: A systematic review. Palliative Medicine. 2022. https://doi.org/10.1177/02692163221083437
  10. Wang J, Wang Y, Tong M, et al. Medical Cannabinoids for Cancer Cachexia: A Systematic Review and Meta-Analysis. BioMed Research International. 2019. https://doi.org/10.1155/2019/2864384
  11. Gundersen TD, Jørgensen N, Andersson AM, et al. Association Between Use of Marijuana and Male Reproductive Hormones and Semen Quality: A Study Among 1,215 Healthy Young Men. American Journal of Epidemiology. 2015. https://doi.org/10.1093/aje/kwv135
  12. Marquardt Filho N, Felkl OR, Veiga DM, et al. Exploring the Association Between Cannabis Use and Male Reproductive Parameters: A Systematic Review and Meta-Analysis. International Brazilian Journal of Urology. 2027. https://pubmed.ncbi.nlm.nih.gov/43012629/
  13. Kasman AM, Thoma ME, McLain AC, Eisenberg ML. Association between use of marijuana and time to pregnancy in men and women: findings from the National Survey of Family Growth. Fertility and Sterility. 2018. https://doi.org/10.1016/j.fertnstert.2018.01.015
  14. Di Forti M, Quattrone D, Freeman TP, et al. The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study. The Lancet Psychiatry. 2019. https://doi.org/10.1016/s2215-0366(19)30048-3
  15. Belladelli F, Del Giudice F, Kasman A, et al. The association between cannabis use and testicular function in men: A systematic review and meta-analysis. Andrology. 2021. https://doi.org/10.1111/andr.12953
  16. Nassan FL, Arvizu M, Mínguez-Alarcón L, et al. Marijuana smoking and markers of testicular function among men from a fertility centre. Human Reproduction. 2019. https://doi.org/10.1093/humrep/dez002
  17. Wise LA, Wesselink AK, Hatch EE, et al. Marijuana use and fecundability in a North American preconception cohort study. Journal of Epidemiology and Community Health. 2018. https://doi.org/10.1136/jech-2017-209755
  18. Nassan FL, Arvizu M, Mínguez-Alarcón L, et al. Marijuana smoking and outcomes of infertility treatment with assisted reproductive technologies. Human Reproduction. 2019. https://doi.org/10.1093/humrep/dez098
  19. Thistle JE, Graubard BI, Braunlin M, et al. Marijuana use and serum testosterone concentrations among U.S. males. Andrology. 2017. https://doi.org/10.1111/andr.12358
  20. Leung J, Chan GCK, Hides L, Hall WD. What is the prevalence and risk of cannabis use disorders among people who use cannabis? a systematic review and meta-analysis. Addictive Behaviors. 2020. https://doi.org/10.1016/j.addbeh.2020.106479
  21. Marconi A, Di Forti M, Lewis CM, Murray RM, Vassos E. Meta-analysis of the Association Between the Level of Cannabis Use and Risk of Psychosis. Schizophrenia Bulletin. 2016. https://doi.org/10.1093/schbul/sbw003
  22. Gunn JKL, Rosales CB, Center KE, et al. Prenatal exposure to cannabis and maternal and child health outcomes: a systematic review and meta-analysis. BMJ Open. 2016. https://doi.org/10.1136/bmjopen-2015-009986
  23. Marchand G, Masoud AT, Govindan M, et al. Birth Outcomes of Neonates Exposed to Marijuana in Utero: A Systematic Review and Meta-analysis. JAMA Network Open. 2022. https://doi.org/10.1001/jamanetworkopen.2021.45653
  24. Asbridge M, Hayden JA, Cartwright JL. Acute cannabis consumption and motor vehicle collision risk: systematic review of observational studies and meta-analysis. BMJ. 2012. https://doi.org/10.1136/bmj.e536
  25. Rogeberg O, Elvik R. The effects of cannabis intoxication on motor vehicle collision revisited and revised. Addiction. 2016. https://doi.org/10.1111/add.13347
  26. Gurney J, Shaw C, Stanley J, et al. Cannabis exposure and risk of testicular cancer: a systematic review and meta-analysis. BMC Cancer. 2015. https://doi.org/10.1186/s12885-015-1905-6
  27. Kardoust Parizi M, Tsuboi I, Matsukawa A, et al. Cannabis use and risk of testicular germ cell tumour: a systematic review and meta-analysis. BJU International. 2026. https://doi.org/10.1111/bju.70062
  28. Jeffers AM, Glantz S, Byers AL, Keyhani S. Association of Cannabis Use With Cardiovascular Outcomes Among US Adults. Journal of the American Heart Association. 2024. https://doi.org/10.1161/jaha.123.030178

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