Review of scientific evidence on effects of medical and non-medical marijuana legalization on public health in the United States

The review is focused on studies designed to identify causal effects of medical and non-medical marijuana legalization on public health outcomes. I searched existing reviews, library databases, and the internet for studies addressing marijuana policy effects, whether peer-reviewed or not, and screened them using the following criteria:

• the type of policy examined,
• the outcomes examined, and
• methodological quality.

The review is limited to studies examining effects of medical marijuana laws (MML) and nonmedical marijuana laws (NMML) in the United States. There is considerable variability in the specific features of MMLs and NMMLs, and this variability is discussed in more detail below as it pertains to conclusions that can be drawn from the extant literature.

The review is limited to studies examining outcomes broadly related to public health. The specific outcomes examined in the final pool of selected studies is largely determined by the availability of data sources that are suitable for state-level policy evaluation - that is, multiyear, multi-state data sources. 

The final pool of studies examined outcomes including:

• youth and adult use of marijuana,
• disordered cannabis use,
• use of other substances including alcohol, tobacco, and opioids,
• health outcomes including overall health, obesity, mental health, suicide, poison control contacts, and emergency department visits,
• traffic safety, and
• workplace safety.