Marijuana legalization continues to generate significant public discussion, progressing from medicinal applications to recreational use in recent years. Public opinion on this matter has shifted substantially over a relatively brief timeframe. However, the debate often overlooks an important consideration: the connection between marijuana consumption and psychotic illnesses including schizophrenia, schizoaffective disorder, and certain types of bipolar disorder. These serious conditions are prevalent throughout Massachusetts and impact numerous individuals and families.
Long-standing research has demonstrated that marijuana use correlates with symptom exacerbation and relapse in those diagnosed with psychotic disorders. More recent and concerning findings suggest that adolescent marijuana use precedes the development of psychotic disorders1. Specifically, teenagers using marijuana on a daily basis face greater odds of later developing a psychotic disorder compared to weekly users, with non-users facing the lowest risk. Notably, this risk appears limited to adolescence and early adulthood; individuals initiating marijuana use in their late 20s or 30s do not show elevated risk for subsequent psychotic disorder diagnosis. The evidence suggests that marijuana use during the critical period of brain development—from birth through age 21 and potentially into the mid-20s—elevates the risk of serious psychiatric illness. While recreational marijuana legalization targets adults, teenagers represent a population particularly vulnerable to problematic use patterns. Increased availability of recreational marijuana would likely result in greater teenage access.
Debate exists within psychiatry and neurology regarding whether marijuana directly “causes” psychotic disorders or functions within more complex disease processes. However, research conclusively demonstrates that individuals who abstain from marijuana use face reduced risk for these conditions. Consequently, lowering marijuana consumption among teenagers and young adults represents a significant public health opportunity. A specific chemical compound in marijuana may ultimately prove responsible, yet absent fuller understanding of these mechanisms and their consequences, I hold serious reservations about the potential harms that expanded recreational marijuana availability could produce for many young people and their families.
Dost Ongur, M.D., Chief, Psychotic Disorders Division at McLean Hospital and Associate Professor of Psychiatry at Harvard Medical School