Since 2014, lawmakers in 16 states have enacted statutes permitting qualified patients limited access to marijuana-derived extracts dominant in the non-psychotropic plant cannabinoid CBD (a.k.a. cannabidiol). While the present movement advocating for legal access to CBD is largely focused on its therapeutic potential to mitigate seizure frequency in patients with epilepsy and other similarly debilitating diseases, scientists have also long been aware of the compound’s anti-psychotic and anxiolytic properties — qualities that may one day lead to its use for the treatment of symptoms of schizophrenia and perhaps other psychiatric illnesses.
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Although scientists first isolated CBD’s chemical structure in 1940, it was not until several decades later that investigators first reported its ability to offset the psychoactive effects of delta-9-THC. For example, a 1974 clinical trial reported that the addition of 60 mg of CBD to 30 mg doses of THC in healthy volunteers was associated with reduced anxiety and greater pleasurable effects as compared to the administration of THC alone. Later clinical trials reported that CBD administration reduced a number of THC-induced adverse effects, such as disconnected thoughts and depersonalization. Separate studies further determined that CBD dosing mitigated dysphoria in subjects with experimentally induced psychotic symptoms.
More recently, investigators have begun to assess the use of CBD in patients diagnosed with schizophrenia. For instance, a 1995 case study reported significant improvement of schizophrenic symptoms in a single patient following four-weeks of daily CBD treatment. The patient’s condition noticeably worsened when treatment was discontinued. A 2006 trial of three subjects with treatment-resistant schizophrenia also reported that CBD dosing was associated with the partial improvement of various outcome measures. In the largest clinical study of its kind to date, a 2012 double-blind, randomized placebo-controlled trial assessing CBD versus the prescription anti-psychotic drug Amisulpride in 42 subjects with schizophrenia and acute paranoia, the authors reported that both treatments were associated with “equally significant clinical improvement,” but that cannabidiol “possessed significantly less side effects.”
Writing in his review article, “Cannabidiol: from an inactive cannabinoid to a drug with a wide spectrum of action,” Brazilian researcher Antonio Zuardi concludes, “[C]linical studies suggest that CBD is an effective, safe and well-tolerated alternative treatment for schizophrenic patients.” Canadian researchers from the University of Western Ontario bolstered this finding earlier this month. The investigative team for the first time identified the neurological pathways whereby CBD exerts its anti-psychotic effects, concluding: “CBD can produce effects similar to antipsychotic medications by triggering molecular signaling pathways associated with the effects of classic antipsychotic medications.”
While a rash of recent media reports have alleged that cannabis use may trigger psychotic episodes in habitual users, a new literature review largely dismisses this claim. Writing in the journal Current Psychiatry Reports, researchers from the University of Wyoming and from Columbia University in New York City evaluated recent studies associating the use of cannabis with psychotic behaviors. They reported that cannabis use probably does not cause psychosis, but rather, that subjects susceptible to the disorder are more likely to engage in early-onset use of the substance. “Evidence reviewed here suggests that cannabis does not in itself cause a psychosis disorder,” they concluded. “Rather, the evidence leads us to conclude that both early use and heavy use of cannabis are more likely in individuals with a vulnerability to psychosis.”
In fact, some observational trials report that patients turn to cannabis use following a diagnosis of a psychiatric disorder, implying that at least some patients may already be self-medicating with the plant. For example, survey data published in the International Journal of Mental Health Nursing found that over half of the study’s respondents reported using cannabis to subjectively control schizophrenic symptoms.
Although the science surrounding CBD as a potential anti-psychotic agency is still in its infancy, the initial research demonstrating the compound’s potential efficacy and adequate side-effect profile is promising. While current anti-psychotic medications are associated with significant side effects and poor treatment adherence, CBD has been shown to be safe and well tolerated in human subjects. Ultimately, however, more research is necessary before patients or physicians can harness the plant’s full potential as a possible psychiatric treatment option.
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