Marijuana Use and Mental Health

Correlation or causation? And in which direction?

A common critique of marijuana legalization asserts that marijuana use causes mental illness. Numerous studies document a correlation between use and conditions such as psychosis. This evidence, however, does not pin down the degree to which use causes, versus results from, reduced mental health. Indeed, mere correlations are consistent with use making pre-existing mental health conditions less severe.

New evidence sheds light on how policy impacts the relation between access to legal marijuana and mental health:

Our research examines how the availability of medical cannabis dispensaries in New York State has affected mental health. …

[M]edical cannabis availability was not associated with self-reported poor mental health for adults overall.… . [M]edical cannabis availability improved self-reported mental health among people aged 65 years and older.

Earlier research produced a similar conclusion based on suicide rates.