Cannabis use disorder is estimated to affect approximately 10% of active cannabis users, with estimates approaching 30%-40% of those using cannabis daily. Cannabis use disorder is defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) as meeting at least 2 of 11 criteria (see Look For section) within the last 12 months. Screening of all adults for harmful substance use is recommended by the US Preventive Services Task Force. Screening should focus on brief questions and not biological specimens. Brief screening surveys about cannabis use have high sensitivity for identifying problematic cannabis use and cannabis use disorder.

Age of initial use is highly correlated with progression to cannabis use disorder. Those using before the age of 16 years are at high risk for developing cannabis use disorder. Use before the age of 18 years is associated with increased motor vehicle accident risk, antisocial behavior, school dropout risk, and polysubstance abuse.

Chronic cannabis use can have physiologic adverse effects. Chronic cannabis users have been shown to be at increased risk for cardiovascular mortality compared to nonusers. Cannabis has been shown to modulate secondary immune response; however, it has not been proven to cause any immune-mediated health risks. Cannabis smoking has not been associated with any smoking-related cancers. The effects of in utero and early childhood exposure to cannabis are largely unknown, and most of the current studies have methodologic flaws. Neurobehavioral effects of chronic, frequent cannabis use include deficits in learning and cognition, but these effects most likely improve after cessation. There is no strong evidence that chronic cannabis use causes psychosocial harm to the user.

Both the use of cannabis and cannabis use disorder are associated with increased risks of mood disorders, anxiety disorders, post-traumatic stress disorder, and personality disorders. Higher rates of cannabis use disorder are found in patients with depression, bipolar disorder, and schizophrenia.

Cannabis use disorder is also highly associated with alcohol use disorder, or another substance use disorder, with rates estimated between 75%-85%. This risk is higher in those with severe cannabis use disorder, compared to those with mild or moderate cannabis use disorder.

Smoking cannabis exposes the respiratory tract to thermal injury and particulate matter, negatively affecting the lungs and bronchi, exacerbating asthma, chronic obstructive pulmonary disease (COPD), and other chronic respiratory diseases.

Related topic: acute cannabis intoxication, synthetic cannabinoid poisoning