Does marijuana use have residual adverse effects on self-reported health measures, socio-demographics and quality of life? A monozygotic co-twin control study in men

ABSTRACT Aims To assess the effects of former heavy marijuana use on selected aspects of health. Design A monozygotic co‐twin control design was used to compare the health of former heavy marijuana using male monozygotic twins to that of their co‐twins who never used marijuana significantly. Setting In‐person survey and questionnaires. Participants Fifty‐six marijuana use discordant monozygotic twin pair members of the Vietnam Era Twin (VET) Registry. Measurements Current socio‐demographic characteristics; current nicotine and alcohol use; life‐time nicotine and alcohol abuse/dependence; past 5‐year physical and mental health services utilization; and health‐related quality of life. Findings The mean number of days on which the marijuana user twin used marijuana in his life‐time was 1085, while the non‐marijuana user used marijuana a maximum of 5 days. Marijuana was last used a mean of 20 years previously. No significant differences were found between the former marijuana user twins and their siblings for current socio‐demographic characteristics; current nicotine or alcohol use; life‐time nicotine or alcohol abuse/dependence; past 5‐year out‐patient or emergency room visits, hospitalizations or medication use for medical problems; past 5‐year mental health out‐patient use or hospitalizations; or health‐related quality of life. Conclusions Previous heavy marijuana use a mean of 20 years earlier by a group of men who reported no other significant illicit drug use does not appear to be associated with adverse socio‐demographic, physical or mental health adverse effects. The conclusions of the study are limited by possible participation and recall biases, relatively small sample size and the absence of a physical health examination.