Cannabis safety: the risks worth knowing

The CDC states that cannabis "may be bad for your baby no matter how you use it — this includes smoking, vaping, dabbing, eating or drinking, and applying creams or lotions to the skin," and links use in pregnancy to lower birth weight and abnormal neurological development, with later problems in attention, memory, problem-solving, and behaviour.

For breastfeeding, the CDC notes THC is stored in body fat and released slowly, so a baby can be exposed even after use has stopped. NASEM independently found substantial evidence associating maternal cannabis smoking with lower birth weight.

ACOG issued updated clinical guidance on cannabis use during pregnancy and lactation in 2025. If you are pregnant or planning to be, that guidance and your obstetrician are the right sources — not this page.

The CDC notes the brain continues developing until around age 25, that using cannabis before 18 may affect how the brain builds connections for attention, memory, and learning, and that those effects "may last a long time or even be permanent."

This is the clearest age-related risk in cannabis, and it is why the 21+ requirement on this site is not a formality.

NASEM found substantial evidence of an association between cannabis use and the development of schizophrenia or other psychoses, with the highest risk among the most frequent users. NIDA notes evidence linking cannabis use to earlier onset of psychosis in people with genetic risk.

NASEM also found substantial evidence associating cannabis use with increased symptoms of mania and hypomania in people diagnosed with bipolar disorder, and with increased incidence of suicidal ideation, suicide attempts, and suicide completion.

If you have a personal or family history of psychosis or bipolar disorder, the risk-benefit calculation is different for you than for the general population.

NASEM found substantial evidence that cannabis use increases the risk of motor vehicle crashes. NIDA notes cannabis is the drug most frequently found in the blood of drivers involved in crashes, including fatal ones — while also noting the evidence on magnitude is mixed, with one NHTSA study finding no significant increase after adjustment.

The honest summary: the association is well established, the size is debated, and impairment is real. Do not drive.

Long-term heavy use can cause cyclical severe vomiting, typically after several years of use, often relieved temporarily by hot bathing. Because cannabis normally relieves nausea, people frequently respond by using more — which makes it worse.

The only definitive treatment is stopping cannabis. Prognosis is good with early recognition.

A study in Annals of Internal Medicine found edibles accounted for 10.7% of cannabis-attributable emergency department visits over a three-year period while representing only 0.32% of total cannabis sales. Edible-related visits more often involved acute psychiatric symptoms and cardiovascular symptoms.

NASEM separately found moderate evidence of increased pediatric overdose injuries in states where cannabis is legal. Store edibles locked and out of reach.

NASEM found substantial evidence that long-term cannabis smoking is associated with worse respiratory symptoms and more frequent chronic bronchitis episodes. Vaporisation avoids combustion products but is not risk-free.