A new study published this week has found that there is little evidence that cannabis is an effective treatment for several mental health conditions and called for more research on the use of cannabinoids for psychiatric care. A report on the research was published on Monday in the journal The Lancet Psychiatry.
For the study, researchers conducted a meta-analysis of the effects of medicinal cannabinoids in clinical trials studying depression, anxiety, attention-deficit hyperactivity disorder (ADHD), Tourette syndrome, post-traumatic stress disorder (PTSD) and psychosis. The research team identified 83 studies involving 3,000 participants that had been conducted between 1980 and 2018 for inclusion in the meta-analysis.
The authors of the study wrote in their interpretation of the analysis that there is little evidence that cannabinoids improved the patients’ conditions.
“There is scarce evidence to suggest that cannabinoids improve depressive disorders and symptoms, anxiety disorders, attention-deficit hyperactivity disorder, Tourette syndrome, post-traumatic stress disorder, or psychosis,” they wrote. “There is very low quality evidence that pharmaceutical THC (with or without CBD) leads to a small improvement in symptoms of anxiety among individuals with other medical conditions.”
The study’s authors also called for more research on psychiatric uses for cannabinoids, noting that proper guidance for such treatment was impossible without it.
“There remains insufficient evidence to provide guidance on the use of cannabinoids for treating mental disorders within a regulatory framework,” they added. “Further high-quality studies directly examining the effect of cannabinoids on treating mental disorders are needed.”
Professor Louisa Degenhardt of the National Drug and Alcohol Research Centre at UNSW Sydney, Australia, the lead author of the study, cautioned practitioners against recommending cannabis before more research can be done.
“In countries where medicinal cannabinoids are already legal, doctors and patients must be aware of the limitations of existing evidence and the risks of cannabinoids,” she said. “These must be weighed when considering use to treat symptoms of common mental health disorders. Those who decide to proceed should be carefully monitored for positive and negative mental health effects of using medicinal cannabinoids.”
Cannabis May Carry Risks for Mental Health Patients
The authors of the study noted that “research suggests that cannabis use can increase the occurrence of depression, anxiety, and psychotic symptom,” risks that should be considered both before and while cannabinoids are used as a treatment for mental health conditions.
“These risks, and the limitations of existing evidence, need to be weighed when considering the use of medicinal cannabinoids to treat symptoms of common mental disorders,” they wrote. “Those who decide to proceed should be carefully monitored for positive and negative mental health effects of using medicinal cannabinoids.”
Deepak Cyril D’Souza of the Yale University School of Medicine said in an opinion piece also published in the journal that “in light of the paucity of evidence, the absence of good quality evidence for efficacy, and the known risk of cannabinoids, their use as treatments for psychiatric disorders cannot be justified at present.”
Harry Sumnall, a professor of substance use at Liverpool John Moores Public Health Institute in the U.K. who was not involved in the study, noted that it’s possible that continued research will determine that cannabis is an effective treatment for some mental health conditions.
“The old adage that absence of evidence doesn’t necessarily mean absence of effectiveness is true here,” he said.