What are the side effects of cannabis use?

Side Effects of Cannabis Use

Cannabis use causes a wide range of adverse effects across multiple organ systems, with the most clinically significant being acute psychosis in vulnerable individuals, cardiovascular events including arrhythmias and myocardial infarction, respiratory disease, cognitive impairment (particularly in verbal learning and memory), and cannabis use disorder affecting approximately 10% of chronic users. 1

Acute Side Effects

Neuropsychiatric Effects

• High doses of THC trigger psychotic symptoms including hallucinations and paranoia, particularly in vulnerable individuals 1
• Mental slowness and impaired reaction times occur commonly during intoxication 2
• Anxiety and accentuation of pre-existing anxiety symptoms are frequently reported 2, 3
• Suicidal ideations and tendencies can emerge acutely 3
• Cannabis intoxication causes small-to-moderate deficits in executive function, with inhibition being most severely impaired 4, 5

Cardiovascular Effects

• Cannabis causes tachycardia, orthostatic hypotension, and arrhythmias through multiple mechanisms including catecholamine reuptake blockade and sympathetic stimulation 1
• Myocardial ischemia can occur in at-risk individuals, even acutely 1
• The drug promotes a prothrombotic state through increased platelet activation and aggregation 1
• Combined use with tobacco produces greater increases in heart rate and vasoconstriction than either substance alone 1

Other Acute Effects

• Impaired coordination and motor performance increase the risk of accidents 2, 3
• Driving under cannabis influence doubles the risk of fatal road accidents 2
• Cannabinoid hyperemesis syndrome presents with cyclical vomiting relieved by hot showers 1

Chronic and Long-Term Side Effects

Cognitive and Neurological Effects

• Verbal learning and memory show the most robust impairment, with deficits persisting beyond acute intoxication 4
• Working memory and decision-making demonstrate small-to-moderate deficits 4
• Regular cannabis use causes structural brain changes, particularly volumetric reductions in the hippocampus and amygdala 6
• Gray matter and white matter alterations occur with chronic use 6
• Downregulation of CB1 receptors develops in regular users 6

Mental Health Effects

• Cannabis use increases risk for developing depressive disorders and may exacerbate existing psychiatric conditions 1
• The relationship between cannabis and psychotic illness shows statistical association in longitudinal studies, though causality remains difficult to establish 2
• Early onset cannabis use, especially weekly or daily use during adolescence, strongly predicts future dependence and is associated with neuropsychological decline 1
• Cannabis may have deleterious effects on adolescent brain development 1

Cardiovascular Disease

• Long-term use is associated with myocardial infarction and stroke 1
• Chronic use causes coronary vasoconstriction and increases endothelin-1 while decreasing nitric oxide 1
• Older adults face higher risk for acute cannabis toxicity presenting with sedation, obtundation, and myocardial ischemia 1

Respiratory Effects

• Cannabis smoking is associated with chronic bronchitis and chronic obstructive pulmonary disease 1
• Lung function impairment occurs with regular smoking 1
• The link to lung cancer remains unclear, confounded by concomitant tobacco use 1
• Vaping cannabis poses unique risks, as demonstrated by the 2019 outbreak of acute lung injury associated with THC concentrate and vitamin E acetate 1

Addiction and Withdrawal

• Approximately 10% of adults with chronic cannabis use develop cannabis use disorder characterized by clinically significant impairment 1
• A randomized trial showed that receiving a medical cannabis card nearly doubled the incidence of cannabis use disorder within 12 weeks 1
• Withdrawal symptoms occur within 48 hours to 3 days after cessation and include sleep disturbances, appetite changes, irritability, anxiety, nervousness, restlessness, aggression, and abdominal pain 1, 2
• Symptoms typically last up to 2-14 weeks 1, 2

Special Population Considerations

Adolescents and Young Adults

• Early cannabis use elevates risk for psychotic disorders in adulthood, depression, and suicidal ideation or behavior 1
• The relationship between poor school performance and early, regular cannabis use creates a vicious circle 2

Older Adults (≥65 years)

• Cannabis use has increased in this population 1
• Higher risk for behavioral health issues including anxiety and depression 1
• Increased cannabis-related emergency department visits with presentations of acute toxicity 1

Pregnancy

• Cannabis use during pregnancy may negatively affect fetal brain development and increase risk for premature birth 1

Critical Caveats

The potency of cannabis products has dramatically increased, with average THC concentration nearly doubling from 9% in 2008 to 17% in 2017, and cannabis concentrates reaching THC levels as high as 70% 1. This increasing potency significantly elevates all health risks 1.

The adverse effects are dose-dependent, with higher THC doses producing more severe effects 1, 2.