There's little evidence to support the use of cannabinoids to treat psychiatric disorders such as depression, anxiety, posttraumatic stress disorder (PTSD), and psychosis, results of a new systematic review and meta-analysis suggest. "Patients who are interested in using cannabinoids for mental disorders should understand that there's limited evidence for it, and if they do choose this intervention, there needs to be monitoring to check that it's helpful and is not causing harm," lead investigator Louisa Degenhardt, PhD, National Drug and Alcohol Research Centre, University of New South Wales, Sydney, Australia, told Medscape Medical News. A large body of evidence shows cannabis use can increase depression, anxiety, and psychotic symptoms, and lead to dependence, she noted. "In many ways, we know more about the long-term risks of regular cannabis use than we do about its benefits for people with mental disorders," said Degenhardt. Meanwhile, she added, the trend toward legalization of cannabis has made it widely available on a global scale. The study was published online today in Lancet Psychiatry. "Notable Absence of Evidence" The investigators point out there is a "notable absence of high-quality evidence where mental disorders are the primary target of [cannabinoid] treatment." Specifically, they note, "medicinal cannabinoids, including medicinal cannabis and pharmaceutical cannabinoids and their synthetic derivatives such as tetrahydrocannabinol (THC) and cannabidiol (CBD) have been suggested to have a therapeutic role in certain mental disorders." However, juxtaposed to the limited evidence base, the authors note "countries are increasingly allowing cannabinoids to be made available for medical purposes, including for the treatment of mental disorders." To shed more light, the investigators conducted what they describe as "the most comprehensive systematic review and meta-analysis examining the available evidence for medicinal cannabinoids in treating mental disorders and symptoms." Researchers carried out an extensive literature search of studies published from January 1980 to April 2018 of any type and formulation of medicinal cannabinoid including THC, CBD, or a combination of both, on various psychiatric conditions. The analysis included 40 randomized controlled trials and more than 3000 adult subjects. Many of these studies were small. For some mental disorders, there was only one randomized controlled trial. In some studies, the psychiatric condition was the primary outcome, but in many cases, it was a secondary outcome, "so there's a lot of scope for more work to be done," Degenhardt noted. The authors categorized the cannabis products into pharmaceutical grade THC, pharmaceutical grade CBD, and "medicinal cannabis" (any part of the cannabis plant and plant material such as buds, leaves or plant extracts). They synthesized the effect of cannabinoids as odds ratios for remission and standardized mean differences (SMDs) for symptom change. Source
