The interplay between marijuana use and mental illness is complicated and full of unanswered questions. How marijuana affects risk of developing psychiatric disease, and conversely, how psychiatric disorders influence marijuana use, are actively being investigated in scientific studies.
Some research suggests that marijuana use by young adults is linked with the onset of psychosis, a mental state characterized by a disconnection from reality that is characteristic of psychiatric disorders like schizophrenia.
From what we currently know, individuals with genetic predisposition to schizophrenia are at particularly high risk of developing psychosis if they use marijuana. In addition, prolonged marijuana use in those with pre-existing schizophrenia can exacerbate disease symptoms.
A link between marijuana and later onset of psychosis was first described in a large 1987 study. In this famous study, researchers found that participants who reported marijuana use before the age of 18 were 2.4 times more likely to develop schizophrenia. Individuals who reported using marijuana 50 or more times were 6 times more likely to develop schizophrenia (Andréasson, Lancet, 1987).
Other studies have found similar results, and marijuana use has consistently been linked to earlier disease onset and a more severe disease (Arseneault, BMJ, 2002; McLaren, Int J Drug Policy, 2010; Volkow, JAMA Psychiatry, 2016).
In people already diagnosed with schizophrenia, continued marijuana has also been shown to worsen symptoms of hallucinations, delusions, and confused thinking (Weiss, Int J Drug Policy, 2017).
As new knowledge emerges, it is essential to stay up to date on how marijuana use interacts with mental health. Oftentimes, the nature of this relationship seems much like the “chicken and the egg” paradox, in that it is often unclear if mental health disorders preceded marijuana use.
If you or a loved one is struggling with mental health in addition to cannabis use disorder, it is best to contact your healthcare provider so that you can navigate a path to treatment.
Weedless.org is a free, web-based resource and community created by a team of healthcare professionals and researchers. We distill the facts about marijuana use and its effects into practical guidance for interested persons or for those who are thinking about or struggling to quit weed. Finding reliable, easy to understand information about marijuana should never be a struggle—that is why our core mission is to provide the most up to date information about marijuana use, abuse, addiction, and withdrawal. While we seek to empower individuals to have control over their use, we are not "anti-weed" and we support efforts to legalize adult marijuana use and study.