Strong evidence
Helps chronic pain in adults
Lessens chemotherapy-induced nausea and vomiting
Relieves some symptoms of multiple sclerosis
Moderate evidence
Relieves sleep problems caused by obstructive sleep apnea syndrome, fibromyalgia, chronic pain, and multiple sclerosis
Doesn’t increase risk of cancers
Limited or no evidence
Counters the loss of appetite associated with HIV/AIDS
Relieves symptoms of anxiety, post-traumatic stress disorder, Tourette’s syndrome, dementia, depression, all cancers, irritable bowel syndrome, epilepsy, Parkinson’s, and schizophrenia

Purported risks

Strong evidence
Worsens respiratory problems, such as chronic bronchitis episodes
Motor-vehicle accidents
Low birth weight in babies
Schizophrenia or other psychoses
Moderate evidence
Injuries, such as respiratory distress, among children who smoke cannabis
Impaired learning, memory, and attention
Social-anxiety disorder, depression, and bipolar episodes in people with diagnosed bipolar disorder
Substance abuse disorder for alcohol, tobacco, and other illicit drugs
Limited or no evidence
Impaired academic performance, educational attainment, or social engagement
Heart attack, stroke, diabetes, anxiety, and bipolar episodes in people not diagnosed with bipolar disorder
Asthma or other chronic obstructive pulmonary diseases (COPD) when controlled for tobacco use
Death from overdose