Using state-level data for the period 1990 through 2007, we estimate the effect of legalizing
medical marijuana on suicide rates. Our results suggest that the passage of a medical
marijuana law is associated with an almost 5 percent reduction in the total suicide rate, an 11
percent reduction in the suicide rate of 20- through 29-year-old males, and a 9 percent
reduction in the suicide rate of 30- through 39-year-old males. Estimates of the relationship
between legalization and female suicides are less precise and are sensitive to functional
form.
Here is the link:
http://ftp.iza.org/dp6280.pdf