Cannabis and Mental Health: A Review.

Abstract

Importance: Cannabis use is common among those with mental health conditions, and many people report using cannabis to manage mental health symptoms. It is important for clinicians to understand the lack of clear benefits of cannabis for mental health conditions and the potential for substantial adverse effects.

Observations: Overall, the potential benefits of cannabis for mental health conditions remain poorly studied. There is low-certainty evidence that Δ-9-tetrahydrocannabinol (THC)-predominant cannabis may not improve symptoms of posttraumatic stress disorder, and there is largely insufficient evidence to characterize the effects of long-term THC-predominant cannabis use on anxiety, depression, and attention-deficit/hyperactivity disorder. There is emerging low-certainty evidence that the cannabis constituent cannabidiol alone may reduce anxiety in patients with anxiety disorders. THC-predominant cannabis use holds substantial risk for adverse mental health effects, and counseling patients about these risks is crucial to promote safety. These risks include worsening mania symptoms and function in those with bipolar disorder and an increase in psychotic symptoms in those with psychotic spectrum disorders. Among people with past-year cannabis use, about 3 in 10 have cannabis use disorder (CUD), and about one-half those with CUD have moderate or severe disease with negative social, employment, or other adverse outcomes. Regular use of high THC-content products by adolescents and young adults is associated with several concerning risks, including an increased risk of psychosis (estimates range from about 2-fold to 11-fold increased risk), a higher risk of CUD, and self-harm in those with mood disorders. Cannabis use should be avoided in individuals at elevated risk of harms, including adolescents and young adults, those with bipolar or psychotic disorders, pregnant individuals, and those at risk for substance use disorders.

Conclusions and relevance: The current evidence base is not sufficient to support the use of cannabis for the treatment of mental health conditions and demonstrates substantial risks of adverse effects. Clinicians should engage patients with mental health conditions in discussions about cannabis use because use is common, has an influence on mental health symptoms, and is likely an important modifiable risk factor for mental health conditions in some populations.