The past decade has seen unprecedented shifts in the cannabis policy environment, and the public health impacts of these changes will hinge on how they affect patterns of cannabis use and the use and harms associated with other substances.,To review existing research on how state cannabis policy impacts substance use, emphasizing studies using methods for causal inference and highlighting gaps in our understanding of policy impacts on evolving cannabis markets.,Narrative review of quasi-experimental studies for how medical cannabis laws (MCLs) and recreational cannabis laws (RCLs) affect cannabis use and use disorders, as well as the use of or harms from alcohol, opioids, and tobacco.,Research suggests MCLs increase adult but not adolescent cannabis use, and provisions of the laws associated with less regulated supply may increase adult cannabis use disorders. These laws may reduce some opioid-related harms, while their impacts on alcohol and tobacco use remain uncertain. Research on RCLs is just emerging, but findings suggest little impact on the prevalence of adolescent cannabis use, potential increases in college student use, and unknown effects on other substance use.,Research on how MCLs influence cannabis use has advanced our understanding of the importance of heterogeneity in policies, populations, and market dynamics, but studies of how MCLs relate to other substance use often ignore these factors. Understanding effects of cannabis laws requires greater attention to differences in short- versus long-term effects of the laws, nuances of policies and patterns of consumption, and careful consideration of appropriate control groups.

If all veterans suffering from major depression and posttraumatic stress disorder were to receive evidence-based treatments, policy simulations suggest that cost savings generated would be $138 million (15 percent) over two years.

This research used microsimulation modeling to estimate the social costs of depression and posttraumatic stress disorder (PTSD) for the 261,827 troops deployed on June 30, 2008, for Operations Enduring Freedom and Iraqi Freedom. Given current standards of care, roughly half of these individuals will be treated for these conditions in the 2 years after they return, and 30% of those treated will receive evidence-based treatment (EBT). Our results suggest that the 2-year social costs of depression and PTSD for this cohort will be $923 million. Policy simulations evaluating the savings associated with universal access to EBT suggest that such access would generate cost savings of $138 million (15%).