What are the long-term effects of cannabis use on a general adult population, particularly those with a history of mental health issues, respiratory problems, or cardiovascular disease?

Long-Term Effects of Cannabis Use

Long-term cannabis use causes significant and potentially irreversible harm across multiple organ systems, with the most concerning effects being psychiatric deterioration (including psychosis and depression), cardiovascular events (myocardial infarction and stroke), cognitive impairment (particularly affecting memory and executive function), and respiratory disease, with risks amplified by early initiation, high-potency products, and pre-existing vulnerabilities. 1

Psychiatric and Neurological Consequences

Mental Health Deterioration

• Cannabis use increases risk for developing depressive disorders and exacerbates existing psychiatric conditions in vulnerable individuals 1
• High doses of THC are specifically associated with psychotic symptoms, with increasing product potency (average THC concentration nearly doubled from 9% in 2008 to 17% in 2017) elevating this risk substantially 1
• Cannabis worsens positive psychotic symptoms and total psychiatric symptoms, with heightened risk for transition to schizophrenia and psychosis 1
• Early onset cannabis use, especially weekly or daily use, strongly predicts future dependence, neuropsychological decline, and elevated risk for psychotic disorders in adulthood 1

Cognitive Impairment

• The most consistent and severe neurological effects occur in verbal learning and memory, attention, and executive function—particularly when use begins during adolescence when the developing brain is most vulnerable 1
• Persistent cognitive deficits develop with regular use, including impaired inhibitory control, decision-making, reduced processing speed, and disrupted connectivity in the prefrontal cortex 1
• Cannabis causes measurable brain alterations including altered gray matter volume, changes in cortical thickness, and specific effects on the orbitofrontal cortex essential for decision-making 1
• Definitive recovery assessment requires at least 6 months of continuous abstinence, representing the minimum timeframe for resolution of cannabis-related neurological effects, with persistent deficits after this period suggesting permanent impairment 1

Cannabis Use Disorder and Withdrawal

• Approximately 10% of adults with chronic cannabis use develop cannabis use disorder, characterized by clinically significant impairment including using more cannabis than expected and difficulty cutting back 1, 2
• Long-term daily users experience non-life-threatening but distressing withdrawal symptoms after cessation, including irritability, restlessness, anxiety, sleep disturbances, appetite changes, and abdominal pain 1, 2
• Withdrawal symptoms typically occur within 3 days after cessation and may last up to 14 days 1, 2

Cardiovascular and Cerebrovascular Effects

Acute and Chronic Cardiovascular Risks

• Long-term cannabis use is associated with adverse cardiovascular events, including myocardial infarction and stroke 1, 3
• Cannabis causes arrhythmias and orthostatic hypotension with both acute and chronic use 1
• The American Heart Association reports that marijuana affects heart rhythm through multiple mechanisms: blocking reuptake of catecholamines, causing sympathetic stimulation, increasing heart rate and blood pressure in a dose-dependent fashion, causing coronary vasoconstriction, increasing endothelin-1 while decreasing nitric oxide, and promoting a prothrombotic state through increased platelet activation and aggregation 1
• Acute cannabis toxicity in older adults is potentially associated with sedation, obtundation, and myocardial ischemia or infarction 1

Combined Substance Use Amplification

• Combined use of marijuana with tobacco results in greater increases in heart rate and vasoconstriction than either substance alone 1
• Cannabis users are more than twice as likely to be involved in motor vehicle crashes, with this risk amplified when combined with alcohol 2

Respiratory System Effects

Pulmonary Complications

• Cannabis smoking affects lung function and is associated with conditions including chronic bronchitis and chronic obstructive pulmonary disease 1
• Conflicting data exist regarding cannabis use and respiratory disease, often confounded by concomitant tobacco use 1
• The link between cannabis smoking and lung cancer remains unclear, though cannabis smoke contains hundreds of compounds 1

Gastrointestinal Effects

Cannabinoid Hyperemesis Syndrome

• Long-standing cannabis use can lead to cannabinoid hyperemesis syndrome, characterized by cyclical emetic episodes that are relieved by hot showers 1, 2
• Treatment focuses on complete cannabis cessation 1, 2

Special Population Vulnerabilities

Adolescents and Young Adults

• Cannabis use has a deleterious effect on adolescent brain development, with rapid brain changes occurring more rapidly in adolescents than adults 1
• The developing adolescent brain shows increased susceptibility to cannabis-induced excitotoxicity and structural damage 1
• Early cannabis use is associated with neuropsychological and neurodevelopmental decline, elevated risk for psychotic disorders in adulthood, higher risk for depression, and suicidal ideation or behavior 1

Older Adults (≥65 years)

• Cannabis use has increased among adults aged 65 years or older, who may be at higher risk for behavioral health issues including anxiety and depression 1
• Cannabis-related emergency department visits among older adults have increased 1
• Given that 40% of patients over 65 take 5-9 medications daily, adding cannabis substantially increases the risk of drug-drug interactions, with very high risk interactions with warfarin, and high risk with buprenorphine and tacrolimus 1

Patients with Mental Health History

• Cannabis should be avoided entirely if there is a history of psychotic episodes or breaks with reality 2
• Patients with bipolar disorder face increased risk of exacerbation of manic and psychotic symptoms, especially with high-dose THC 4
• Patients with a history of substance use disorder are at substantially higher risk for problematic cannabis use 2

Pregnancy

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

Critical Clinical Pitfalls

Increasing Potency Hazard

• The dramatically increasing potency of cannabis products significantly elevates all health risks, with cannabis concentrates potentially containing THC levels as high as 70% 1, 2
• This escalating potency intensifies adverse health effects across all organ systems 1

Vaping-Specific Risks

• Vaping cannabis poses unique risks, as demonstrated by the 2019 outbreak of acute lung injury associated with THC concentrate and vitamin E acetate 1

Drug Interactions

• Cannabis can cause pharmacokinetic drug-drug interactions with commonly used medications including warfarin, buprenorphine, and tacrolimus 2
• Concurrent opioid use increases risk for pharmacodynamic drug-drug interactions 2

Hepatotoxicity with CBD

• CBD-containing products pose a dose-dependent risk of hepatotoxicity, with nearly 6-fold increase in liver enzyme elevation reported 2
• No cases of hepatotoxicity occurred in adults using total CBD doses below 300 mg/day 2

Impairment Duration

• Cognitive and physical impairment is likely up to 12 hours depending on the type of cannabis product, and driving should be avoided during this period 2