Who Should Avoid Medical Cannabis

Part of being a thoughtful evaluation platform is being willing to tell people the truth: cannabis isn't right for everyone. The conditions and circumstances below represent the strongest signals from the published medical literature that medical cannabis should be avoided, used only with extreme caution, or considered only after other options have been thoroughly explored.

Pregnancy and breastfeeding

Both the FDA and ACOG (the American College of Obstetricians and Gynecologists) strongly recommend against cannabis use during pregnancy and breastfeeding.

• THC crosses the placenta and reaches the developing fetus. It also passes into breast milk and can remain there for weeks.
• Prenatal cannabis exposure has been associated with lower birth weight, neonatal complications, and longer-term effects on attention and learning.
• There is no established "safe" dose during pregnancy, and the long-term developmental data continues to grow more concerning, not less.
• If you're pregnant, planning a pregnancy, or breastfeeding, this is one of the clearest "not now" situations.

Children, teens, and young adults under 25

The adolescent and young-adult brain is still actively developing — particularly the prefrontal cortex, which governs judgment, impulse control, and planning — into the mid-twenties.

• Regular THC use before age 25 is associated with measurable changes in IQ, memory, and attention that may not fully reverse after stopping.
• Risk of cannabis use disorder is significantly higher when use begins in adolescence.
• Risk of triggering a first psychotic episode in vulnerable individuals is also age-dependent — meaningfully higher in the teens and early twenties.
• Pediatric medical cannabis (e.g., Epidiolex for severe seizure disorders) is a different conversation — those are FDA-approved medications used under specialist supervision, not the same as general medical cannabis programs.

Personal or family history of psychotic disorders

This is the single strongest psychiatric contraindication in the literature.

• THC can trigger acute psychotic symptoms in vulnerable individuals, and high-potency THC may accelerate the onset of schizophrenia in those already at risk.
• A personal history of schizophrenia, schizoaffective disorder, or psychosis (drug-induced or otherwise) is generally considered a contraindication to THC-containing products.
• A strong family history (first-degree relative with schizophrenia or psychotic disorder) is a serious "proceed only with great caution" signal.

CBD-only products are sometimes considered for patients in this group, but only under careful psychiatric oversight.

Serious cardiovascular disease

Cannabis acutely increases heart rate and can affect blood pressure.

• Recent heart attack, unstable angina, severe arrhythmia, or uncontrolled heart failure are all situations where cannabis use may carry significant risk.
• Older adults with multiple cardiovascular risk factors should have a careful cardiology-informed conversation before starting.
• Smoked or vaped products carry additional cardiovascular and respiratory risk over oral products.

Severe respiratory conditions

Smoked cannabis irritates the airways and is associated with chronic bronchitis symptoms in regular users. Vaped products are not risk-free — the 2019 EVALI outbreak is a reminder of that.

• Patients with severe COPD, severe asthma, or other significant lung disease should generally avoid inhaled forms.
• Oral or sublingual preparations may be more appropriate when cannabis is being considered for these patients.

Active substance use disorders

Roughly 9% of adults who use cannabis develop cannabis use disorder. That number rises to about 17% if use begins in adolescence, and higher still in patients with other active substance use disorders.

• Active opioid, alcohol, or stimulant use disorder may make cannabis use disorder more likely and may interfere with recovery.
• Patients in early recovery should discuss carefully with both their physician and their addiction medicine team before considering cannabis.

High-risk drug-interaction situations

Some medication regimens make cannabis particularly risky to add without specialist input:

• Warfarin and other anticoagulants — bleeding-risk monitoring becomes critical.
• Tacrolimus, cyclosporine, and other transplant immunosuppressants — interactions can affect rejection risk.
• Active chemotherapy regimens — interactions vary by agent and should be reviewed by oncology.
• Patients on multiple sedating medications — additive sedation can be dangerous, especially in older adults.

How to think about your situation

If anything on this page applies to you, that doesn't automatically mean cannabis is off the table — it means the conversation needs to be more careful, more individualized, and more honest.

• Some contraindications are absolute (active pregnancy, history of psychosis with THC).
• Many are relative — weighed against the severity of your symptoms and what other options exist.
• A licensed physician is the right person to make that call, with your input.

The goal of MMDOCSC is to make those evaluations thoughtful and unhurried — including the evaluations that end with "not the right tool for you, here's what might be." That's part of practicing medicine honestly.