What are the health risks of ingesting marijuana, particularly for a patient with a history of substance use and potential eligibility for lung cancer screening?

Health Risks of Ingesting Marijuana

For a patient with substance use history considering lung cancer screening, ingesting marijuana carries significant risks including cannabis use disorder (affecting ~10% of chronic users), psychiatric complications (psychosis, anxiety, depression), cannabinoid hyperemesis syndrome, cardiovascular events, cognitive impairment, and potential drug-drug interactions—risks that are particularly elevated in individuals with pre-existing substance use disorders. 1, 2

Addiction and Substance Use Disorder Risk

• Cannabis use disorder develops in approximately 10% of adults with chronic use, characterized by clinically significant impairment including using more cannabis than expected and difficulty cutting back 1, 2
• Patients with a history of substance use disorder are at substantially higher risk for problematic cannabis use, as explicitly noted in ASCO guidelines 3
• A randomized trial demonstrated that participants receiving a medical cannabis card had almost twice the incidence of developing cannabis use disorder within 12 weeks compared to controls 2
• Early onset of cannabis use, especially weekly or daily use, strongly predicts future dependence 2

Psychiatric and Neurological Complications

Acute Psychiatric Effects

• High doses of THC are associated with severe psychotic symptoms and anxiety, particularly in vulnerable individuals, with moderate to high strength of evidence 1, 2
• Cannabis should be avoided entirely if there is a history of psychotic episodes or breaks with reality 1
• Cannabis use may exacerbate existing psychiatric disorders in vulnerable individuals 2

Chronic Cognitive Effects

• Chronic cannabis use causes impaired verbal learning and memory, deficits in attention and executive function, reduced processing speed, and disrupted connectivity in the prefrontal cortex affecting decision-making 1, 2
• These cognitive deficits are particularly severe when use begins during adolescence when the developing brain is most vulnerable 2
• Cannabis causes measurable brain alterations including altered gray matter volume, changes in cortical thickness, and disrupted prefrontal cortex connectivity 2

Gastrointestinal Complications

• Cannabinoid hyperemesis syndrome is an increasingly recognized consequence of long-standing cannabis use, characterized by cyclical emetic episodes relieved by hot showers 1, 2
• Treatment requires complete cannabis cessation 1, 2
• This syndrome can be particularly distressing and lead to increased healthcare utilization 1

Cardiovascular Risks

• Cannabis use is associated with adverse cardiovascular events including arrhythmias, orthostatic hypotension, myocardial infarction, and stroke 1, 2
• Cannabis affects heart rhythm through multiple mechanisms: blocking catecholamine reuptake, causing sympathetic stimulation, increasing heart rate and blood pressure dose-dependently, causing coronary vasoconstriction, and promoting a prothrombotic state 2
• Long-term cannabis use is specifically associated with myocardial infarction and stroke 2

Hepatotoxicity

• CBD-containing products pose a dose-dependent risk of hepatotoxicity, with nearly 6-fold increase in liver enzyme elevation reported 1
• Importantly, no cases of liver enzyme elevation occurred in adults using total CBD doses below 300 mg/day 1
• ASCO guidelines recommend against using 300 mg or more per day of oral CBD due to lack of proven efficacy and risk for reversible liver enzyme abnormalities 3

Withdrawal Syndrome

• Long-term daily cannabis users experience non-life-threatening but distressing withdrawal symptoms after cessation, including irritability, restlessness, anxiety, sleep disturbances, appetite changes, and abdominal pain 1, 2
• Symptoms typically occur within 3 days and last up to 14 days 1, 2

Drug-Drug Interactions

• Cannabis can cause pharmacokinetic drug-drug interactions with commonly used medications including warfarin, buprenorphine, and tacrolimus 3
• Concurrent opioid use increases risk for pharmacodynamic drug-drug interactions 3
• Administration of oral cannabinoids with high-fat meals significantly increases their absorption 3

Functional Impairment and Safety

• Cannabis users are more than twice as likely to be involved in motor vehicle crashes, with this risk amplified when combined with alcohol 1, 2
• Driving should be avoided while under the influence of cannabis, and cognitive/physical impairment is likely up to 12 hours depending on the type of cannabis product 3
• The 2024 ASCO guideline emphasizes that while cannabis overdoses do not cause respiratory depression like opioids, they can be distressing and place individuals at high risk for falls and healthcare utilization 1

Respiratory Considerations (Relevant for Lung Cancer Screening Context)

• Edible consumption avoids the respiratory risks associated with smoking, which is particularly important for patients being considered for lung cancer screening 1
• Smoking cannabis is associated with chronic bronchitis, chronic obstructive pulmonary disease, and potentially lung cancer, though the link with lung cancer remains unclear and is confounded by tobacco use 2, 4, 5
• The safest administration of cannabis for lung health is oral 4

Cancer Risk

• No clear evidence demonstrates that cannabis use increases risk of lung cancer, although the association between cannabis use and cancer development remains unclear 1
• Low-strength evidence suggests a possible link between marijuana use (>10 years) and testicular germ cell tumors, particularly nonseminoma subtype 6

Special Considerations for This Patient Population

Substance Use History

• The ASCO guidelines explicitly state that substance use disorder history may predispose one to problem cannabis use in the cancer setting 3
• This patient's history of substance use substantially elevates their risk for developing cannabis use disorder 3, 1

Lung Cancer Screening Eligibility

• While cannabis use itself is not a contraindication to lung cancer screening, the patient's substance use history and potential for cannabis use disorder should be addressed 3
• If cannabis is used, oral ingestion is strongly preferred over smoking to avoid additional respiratory harm 1, 4

Clinical Approach

When patients use cannabis outside of evidence-based indications, clinicians should explore goals, educate, and seek to minimize harm 3. For this patient specifically:

• Screen for cannabis use disorder symptoms (using more than expected, difficulty cutting back, clinically significant impairment) 1, 2
• Monitor for psychiatric symptoms, particularly psychosis, anxiety, and depression 1, 2
• Assess for cannabinoid hyperemesis syndrome if gastrointestinal symptoms develop 1, 2
• Evaluate cardiovascular risk factors and monitor for cardiovascular events 1, 2
• Check liver enzymes if CBD doses approach or exceed 300 mg/day 1
• Counsel on driving safety and functional impairment lasting up to 12 hours 3
• Strongly recommend oral ingestion over smoking given lung cancer screening context 1, 4
• Consider referral to addiction medicine if cannabis use disorder develops 3