Cannabis as a treatment for, and cause of, psychiatric disorders
Mental health problems – such as anxiety, depression, and PTSD – are among the most common reasons patients seek out medical cannabis. There is an understandable interest in using cannabis and cannabinoids to treat psychiatric disorders. Preclinical studies suggest that the endocannabinoid system plays a prominent role in modulating feelings of anxiety, mood, and fear. As with opioids and chronic pain management, there is hope that medical cannabis may provide a means of reducing prescription anxiolytics and their associated risks.
The authors of the first systematic review (BMC Psychiatry. 2020 Jan 16;20[1]:24) of the use of medical cannabis for major psychiatric disorders noted that the current evidence was “encouraging, albeit embryonic.”
Meta-analyses have indicated a small but positive association between cannabis use and anxiety, although this may reflect the fact that patients with anxiety sought out this treatment. Given the risks for substance use disorders among patients with anxiety, CBD may present a more viable option. Positive results have been shown as treatment for generalized social anxiety disorder.
Limited but encouraging results have also been reported regarding the alleviation of PTSD symptoms with both cannabis and CBD, although the body of high-quality evidence hasn’t notably progressed since 2017, when NASEM declared that the evidence was insufficient. Supportive evidence is similarly lacking regarding the treatment of depression. Longitudinal studies suggest that cannabis use, particularly heavy use, may increase the risk of developing this disorder. Because THC is psychoactive, it is advised that it be avoided by patients at risk for psychotic disorders. However, CBD has yielded limited benefits for patients with treatment-resistant schizophrenia and for young people at risk for psychosis.
The use of medical cannabis for psychiatric conditions requires a complex balancing act, inasmuch as these treatments may exacerbate the very problems they are intended to alleviate.
Marta Di Forti, MD, PhD, professor of psychiatric research at Kings College London, has been at the forefront of determining the mental health risks of continued cannabis use. In 2019, Dr. Di Forti developed the first and only Cannabis Clinic for Patients With Psychosis in London where she and her colleagues have continued to elucidate this connection.
Dr. Di Forti and colleagues have linked daily cannabis use to an increase in the risk of experiencing psychotic disorder, compared with never using it. That risk was further increased among users of high-potency cannabis (≥10% THC). The latter finding has troubling implications, because concentrations of THC have steadily risen since 1970. By contrast, CBD concentrations have remained generally stable. High-potency cannabis products are common in both recreational and medicinal settings.
“For somebody prescribing medicinal cannabis that has a ≥10% concentration of THC, I’d be particularly wary of the risk of psychosis,” said Dr. Di Forti. “If you’re expecting people to use a high content of THC daily to medicate pain or a chronic condition, you even more so need to be aware that this is a potential side effect.”
Dr. Di Forti noted that her findings come from a cohort of recreational users, most of whom were aged 18-35 years.
“There have actually not been studies developed from collecting data in this area from groups specifically using cannabis for medicinal rather than recreational purposes,” she said.
She added that she personally has no concerns about the use of medical cannabis but wants clinicians to be aware of the risk for psychosis, to structure their patient conversations to identify risk factors or family histories of psychosis, and to become knowledgeable in detecting the often subtle signs of its initial onset.
When cannabis-associated psychosis occurs, Dr. Di Forti said it is primarily treated with conventional means, such as antipsychotics and therapeutic interventions and by refraining from using cannabis. Achieving the latter goal can be a challenge for patients who are daily users of high-potency cannabis. Currently, there are no treatment options such as those offered to patients withdrawing from the use of alcohol or opioids. Dr. Di Forti and colleagues are currently researching a solution to that problem through the use of another medical cannabis, the oromucosal spray Sativex, which has been approved in the European Union.