http://goo.gl/huXAJV
States that implemented medical marijuana laws appear to have lower annual opioid analgesic overdoses death rates (both from prescription pain killers and illicit drugs such as heroin) than states without such laws although the reason why is not clear.
States with medical marijuana laws had a 24.8 percent lower average annual opioid overdose death rate compared to states without such laws. In 2010, that translated to about 1,729 fewer deaths than expected. The years after implementation of medical marijuana laws also were associated with lower overdose death rates that generally got stronger over time: year 1 (-19.9 percent), year 2 (-25.2 percent), year 3 (-23.6 percent), year 4 (-20.2 percent), year 5 (-33.7 percent) and year 6 (-33.3 percent).