ADHD News & Research

‘Scarce Evidence’ of Cannabinoid Effectiveness in Treating ADHD, Mental Disorders: Study

Scientists say more high-quality research is needed to study the efficacy of treating mental disorders with cannabinoids; this was their conclusion after conducting a review of 83 studies on its use in treating six mental disorders.

November 6, 2019

Are cannabinoids effective in treating attention deficit hyperactivity disorder and other mental disorders? According to a study recently published in Lancet Psychiatry1, there is insufficient evidence to suggest so — and more research is needed.

These new findings emerge from a systematic review of more than 80 studies on medicinal cannabinoids and its use in treating six mental disorders: ADHD, depression, anxiety, Tourette syndrome, PTSD, and psychosis. The researchers said the review was prompted by recent interest in the use of cannabinoids, which include synthetic derivatives such as tetrahydrocannabinol (THC) and cannabidiol (CBD), as therapeutic agents for these mental disorders.

“There is a notable absence of high-quality evidence to properly assess the effectiveness and safety of medicinal cannabinoids,” Louisa Degenhardt, a drug and alcohol expert at the University of New South Wales in Australia who co-authored the study, told Reuters2. She added: “Until evidence from randomized controlled trials is available, clinical guidelines cannot be drawn up around their use in mental health disorders.”

The 83 studies included in the review were conducted between 1980 and 2018 and cover 3,067 people. Most of the studies focused on treating depression and anxiety (42 and 31, respectively) with cannabinoids. Only three ADHD studies were included in the review.

The researchers found that use of pharmaceutical THC (with or without CBD) did not significantly affect any of the primary outcomes associated with the mental disorders, but it increased the number the people who reported negative side effects, according to several analyzed studies.

The same product, according to one of the analyzed studies, worsened the symptoms of psychosis. In other studies, it improved anxiety symptoms, though the researchers said this was “very low-quality evidence.”

Few of the studies in the review examined the role of pharmaceutical CBD or medicinal cannabis.

“There remains insufficient evidence to provide guidance on the use of cannabinoids for treating mental disorders within a regulatory framework,” the review concludes. “Further high-quality studies directly examining the effect of cannabinoids on treating mental disorders are needed.”

View Article Sources

1 Black, N. Stockings, E. et. al. (October 28, 2019). Cannabinoids for the treatment of mental disorders and symptoms of mental disorders: a systematic review and meta-analysis. The Lancet Psychiatry. DOI: Retrieved from:

2 Kelland, K. (October 28, 2019). Medicinal cannabis not proven in mental health, study finds. Reuters. Retrieved from:

3 “What You Need to Know (And What We’re Working to Find Out) About Products Containing Cannabis or Cannabis-derived Compounds, Including CBD.” FDA. (Nov. 2019)