Is Medical Cannabis Right for Me?
Learn how to determine if medical cannabis is the right choice for you with this comprehensive guide.
Short answer
Medical cannabis can cause dry mouth, drowsiness, dizziness, impaired memory, and a fast heartbeat. Risk rises with THC dose, daily use, and young age at first use. Cannabis interacts with blood thinners, seizure medicines, and other prescription drugs. Some people should not use it at all.
Common side effects
Most side effects appear within 30 minutes of smoking or vaping and within 1 to 3 hours of eating an edible. Oral use lasts longer because the liver converts THC to a stronger metabolite.
- Dry mouth
- Drowsiness and fatigue
- Dizziness and poor balance
- Short-term memory problems
- Slower reaction time
- Increased appetite
- Red eyes
- Anxiety, paranoia, or panic
- Fast or pounding heartbeat
- Nausea
THC drives most of these effects. CBD causes fewer. High-dose oral CBD can raise liver enzymes and cause sleepiness.
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Serious risks
Cannabis use disorder
About 3 in 10 people who use cannabis develop cannabis use disorder, per the CDC. Signs include using more than planned, failed attempts to cut back, and continued use despite problems at work or at home.
medical cannabis side effects and risks
Psychosis
Daily use of high-THC products links to a higher risk of psychotic disorders. A 2019 review in The Lancet Psychiatry found the strongest link in people who used daily and used products with THC above 10%. People with a personal or family history of schizophrenia or bipolar disorder face the highest risk.
Heart and blood vessels
THC can raise heart rate by 20 to 50 beats per minute within minutes of use. Case reports link cannabis to heart attack, arrhythmia, and stroke in younger adults with no other risk factors. Risk is highest in the first hour after use.
Cannabinoid hyperemesis syndrome
Long-term daily users can develop repeated vomiting, belly pain, and nausea. Hot showers give short-term relief. Symptoms stop after quitting. Rates vary by study and by clinical setting.
Lung and airway
Smoked cannabis delivers tar and irritants. Regular smoking links to chronic bronchitis, cough, and phlegm. Evidence on lung cancer is mixed.
Vaping
In 2019 the CDC counted 2,807 hospitalizations and 68 deaths from EVALI, a lung injury tied to vitamin E acetate in black market vape carts.
Who faces the most risk
- People under 25. The brain is still developing.
- Pregnant and breastfeeding people.
- People with a history of psychosis or bipolar disorder.
- People with heart disease or a prior heart attack.
- Older adults, due to falls and drug interactions.
Drug interactions
Cannabinoids share liver enzymes with many drugs, in particular CYP3A4 and CYP2C9. CBD can raise blood levels of clobazam, warfarin, and some immunosuppressants. Check every prescription with a pharmacist before you start.
Pregnancy and breastfeeding
ACOG and the AAP advise against cannabis in pregnancy and while breastfeeding. Studies link use to low birth weight and preterm birth.
Lower your risk
- Start with a low THC dose. Wait at least 2 hours before taking more.
- Avoid daily use.
- Do not drive for 4 to 6 hours after use.
- Buy from licensed stores. Labels on unregulated products can be wrong.
- Store away from children and pets.
When to call a doctor
Chest pain, a racing heartbeat that does not stop, severe vomiting, confusion, or thoughts of self-harm need medical care. Call 911 for chest pain or trouble breathing.