Does the legalization of medical marijuana increase completed suicide?

Suicide is among the 10 most common causes of death in the United States. Researchers have identified a number of factors associated with completed suicide, including marijuana use, and increased land elevation. Colorado is an ideal state to test the strength of these associations. The state has a completed suicide rate well above the national average and over the past 15 years has permitted first the medical and, as 2014, the recreational use of marijuana.

To determine if there is a correlation between medical marijuana use, as assessed by the number of medical marijuana registrants and completed suicides per county in Colorado.

The number of medical marijuana registrants was used as a proxy for marijuana use. Analysis variables included total medical marijuana registrants, medical marijuana dispensaries per county, total suicide deaths, mechanism of suicide death, gender, total suicide hospitalizations, total unemployment, and county-level information such as mean elevation and whether the county was urban or rural. Analysis was performed with mixed model Poisson regression using generalized linear modeling techniques.

We found no consistent association between the number of marijuana registrants and completed suicide after controlling for multiple known risk factors for completed suicide.

The legalization of medical marijuana may not have an adverse impact on suicide rates. Given the concern for the increased use of marijuana after its legalization, our negative findings provide some reassurance. However, this conclusion needs to be examined in light of the limitations of our study and may not be generalizable to those with existing severe mental illness. This finding may have significant public health implications for the presumable increase in marijuana use that may follow legalization.