Marijuana’s ability to cause psychosis is one of its longest-known and best-documented side effects.
By Erik Messamore, M.D., Ph.D., | Associate professor of psychiatry at Northeast Ohio Medical University
The Alabama legislature is considering a medical marijuana bill that would approve cannabis as a treatment for schizophrenia or other forms of psychosis. This is a bit like recommending cigarettes to treat lung cancer. Cannabis can actually cause psychosis and usually worsens the symptoms of schizophrenia. If passed in its current form, Senate Bill 236 would be uniquely dangerous for the mental health of Alabamians.
Psychosis is a neurological condition that causes the brain to form inaccurate perceptions. Symptoms of psychosis include unusual beliefs (delusions) or sensations (hallucinations). Paranoid, grandiose or other peculiar beliefs can arise from flawed perceptions of things or events in the physical world. Hallucinations occur when the brain misperceives its internal thoughts or feelings. Psychosis is very common, probably because the neurological work of constructing consciousness is far more demanding than it feels to us. About 1 in 11 Americans will experience some facet of psychosis during their lifetime. Psychosis is often temporary but can be more or less persistent in schizophrenia, which affects about one of every hundred people.
Marijuana’s ability to cause psychosis is one of its longest-known and best-documented side effects. Medical textbooks from 19th century America recognized the medicinal value of cannabis, but they also routinely warned of psychosis as a side effect. These days, scientists can easily cause people to experience psychosis in the laboratory simply by dosing people with THC, the main active ingredient in cannabis. An 8 mg dose of THC (a dose someone would get from smoking a single joint) can produce mild psychosis and cognitive impairment. Meanwhile, surveys suggest that about 15% of people who use cannabis will experience symptoms of psychosis. Cannabis can cause psychosis. And it’s clearly linked to schizophrenia.
Regular cannabis users are about four times more likely to develop schizophrenia, and the risk increases in proportion to cannabis exposure. No less than 10 separate peer-reviewed studies have confirmed this relationship. The cannabis-schizophrenia connection makes sense biochemically since cannabis affects the same neurotransmitters, dopamine and glutamate, that are affected in schizophrenia. Many of the behavioral and physiological changes of schizophrenia can be replicated in rats by giving them THC, and cannabis significantly worsens schizophrenia symptoms in those affected by the illness. The National Academies of Sciences Engineering and Medicine found substantial evidence of association between cannabis use and the development of schizophrenia. And the cannabis-friendly Government of Canada requires that cannabis packages carry a warning label stating that regular use of cannabis can increase the risk of psychosis and schizophrenia. Almost no one in medicine believes that cannabis is a schizophrenia medication.
If passed, Senate Bill 236 would officially (and exuberantly) recognize 31 different diseases – from psoriasis to schizophrenia – as treatable by cannabis. All medicines have risks, and a medicine powerful enough to treat 31 diseases surely has risks. The privilege of declaring the medical value of any treatment comes with the moral obligation to also declare its risks and to inform consumers. Even tobacco companies are held to this standard. Yet Senate Bill 236 says nothing about risk.
There are good arguments for decriminalizing or even legalizing cannabis. And there are good arguments to make it available to well-informed patients who could be helped by it. But in seeking to approve cannabis as an effective treatment for schizophrenia, Senate Bill 236 sends a dangerously confusing message to the public about one of marijuana’s most clearly established adverse effects. Alabama's medical marijuana bill would benefit from a more careful consideration of cannabis risks.
Erik Messamore, M.D., Ph.D., is an associate professor of psychiatry at Northeast Ohio Medical University, where he serves as the medical director for the university’s Best Practices in Schizophrenia Treatment Center.