By Dost Ongur, M.D.,
Chief, Psychotic Disorders Division at McLean Hospital and Associate Professor of Psychiatry at Harvard Medical School
There is ongoing public debate about legalization of marijuana – first for medicinal and more recently for recreational uses. Societal attitudes towards this issue have changed dramatically in a relatively short period of time. One issue that is not sufficiently addressed in this debate is the relationship between marijuana use and psychotic disorders such as schizophrenia, schizoaffective disorder, and some forms of bipolar disorder. These are common and severe conditions that affect many lives and families in Massachusetts.
There has long been evidence that marijuana use is associated with relapse and worsening of symptoms for individuals with psychotic disorders. More recent and disturbing evidence indicates that marijuana use in teenage years is associated with subsequent emergence of psychotic disorders1. In fact, teenagers who use marijuana daily are at higher risk of later being diagnosed with a psychotic disorder than those who use weekly. Those who do not use are at lowest risk. In addition, this vulnerability appears to be specific to adolescence and early adulthood; individuals who use marijuana in their late 20s and 30s are not at higher risk of later being diagnosed with a psychotic disorder. This evidence indicates that marijuana use during brain development (at least from birth until age 21 but likely into one’s mid-20s) increases risk for major psychiatric conditions. Although legal recreational marijuana use is not intended for teenagers, this population is at high risk for problem marijuana use. Expanding access to recreational marijuana can be reasonably expected to lead to increased access to marijuana by teenagers.
There is debate among psychiatrists and neurologists about whether marijuana use can be said to directly “cause” psychotic disorders or is part of larger complex disease mechanisms. But the research is quite clear about one thing: people who avoid using marijuana are at lower risk for these
conditions. Therefore, reduction of teenager and young adult marijuana use is a compelling public health intervention. It is possible that one of the chemicals within marijuana is specifically to blame. But until we know more about this issue and understand its implications, I remain concerned about the adverse outcomes from the increased availability of recreational marijuana for many young people and their families.