Heavy cannabis use is the most modifiable risk factor for the onset and poor outcomes of psychotic disorders, though the biological mechanisms underlying individual susceptibility remain unknown. The authors argue that this demands a clear move toward primary and secondary prevention interventions to reduce the impact of heavy cannabis use on the incidence and prevalence of psychotic disorders.
Sexual minority youth (SMY) and heterosexual youth differ in substance use rates, with SMY-females showing higher use of cannabis, ecstasy/MDMA, and hallucinogens at age 17, and also tobacco and stimulants by age 20. SMY-males reported lower tobacco and cannabis use at age 17 but higher ecstasy/MDMA and hallucinogen use at age 20. Psychosocial factors such as internalizing symptoms, self-control, and peer influences partly explain these differences. The findings highlight the need for targeted prevention, especially for SMY-females early in life.
Frequent cannabis use in young adulthood predicts increases in psychotic-like experiences, internalizing symptoms, aggression, problematic substance use, and higher odds of not being in employment, education, or training, along with decreased general well-being from ages 20 to 24. These associations held whether cannabis exposure was measured by self-reported frequency or by hair THC concentrations, and effect sizes were small. Composite measures combining self-reports and hair data were no more informative than either source alone. The findings come from a community sample of 863 young adults, with 150 reporting weekly-to-daily use and 110 having detectable cannabis in hair at age 20.