In 1996, California became the first US state to legalise marijuana use for medical purposes. Medical marijuana is now legal in 29 states. Opponents of medical marijuana argue that such laws increase recreational marijuana use among adolescents, while advocates contend that medical marijuana helps to address the US opioid crisis by reducing overdose deaths.
Two papers published today in the scientific journal Addiction look at the current evidence of the effects of medical marijuana laws and conclude that there is little support for either claim.
The first claim, that legalizing medical marijuana increases recreational use among adolescents, is addressed by a new meta-analysis that pooled the results of eleven separate studies of data from four large-scale US surveys dating back as far as 1991. Results of the meta-analysis indicate that no significant changes (increases or decreases)…