Abstract and Introduction
A total of 1,215 young Danish men aged 18–28 years were recruited between 2008 and 2012 when they attended a compulsory medical examination to determine their fitness for military service. The participants delivered a semen sample, had a blood sample drawn, and underwent a physical examination. They responded to questionnaires including information on marijuana and recreational drug use during the past 3 months (no use, use once per week or less, or use more than once per week). A total of 45% had smoked marijuana within the last 3 months. Regular marijuana smoking more than once per week was associated with a 28% (95% confidence interval (CI): −48, −1) lower sperm concentration and a 29% (95% CI: −46, −1) lower total sperm count after adjustment for confounders. The combined use of marijuana more than once per week and other recreational drugs reduced the sperm concentration by 52% (95% CI: −68, −27) and total sperm count by 55% (95% CI: −71, −31). Marijuana smokers had higher levels of testosterone within the same range as cigarette smokers. Our findings are of public interest as marijuana use is common and may be contributing to recent reports of poor semen quality.
Marijuana is the most widely used illicit recreational drug in the Western world with reported use among 13.7% in the United States and 17.6% in Denmark in 2012 and 2013[1,2] and users being predominantly males. In most countries, marijuana is still an illegal drug, yet more and more countries are legalizing marijuana for recreational use. The active component of marijuana is Δ9 -tetrahydrocannabiol, which has been shown to have receptors in both the brain and the testis. Over the past years, marijuana has been found to affect the brain, increasing the risk of psychotic disorders, and to change hormone levels: Chronic abuse of marijuana can lead to cognitive deficits.[3,5] Yet few studies have investigated the association between marijuana and male reproduction. Previous studies have been conducted among men attending infertility clinics, or in small populations of chronic users, and among men suffering from malnutrition and using other recreational drugs.[6–8]
We therefore studied the association between marijuana use and semen quality and hormone levels among 1,215 young, healthy, unselected men of whom 45.4% had used marijuana during the past 3 months.
Am J Epidemiol. 2015;182(6):473-481. © 2015 Oxford University Press