Painkiller abuse and overdose are lower in states with medical marijuana laws. When medical marijuana is available, pain patients are increasingly choosing pot over powerful and deadly prescription narcotics. Now a new study [provides] clear evidence of a missing link in the causal chain running from medical marijuana to falling overdoses. Researchers at the University of Georgia scoured the database of all prescription drugs paid for under Medicare Part D from 2010 to 2013. In the 17 states with a medical-marijuana law in place by 2013, prescriptions for painkillers and other classes of drugs fell sharply compared with states that did not have a medical-marijuana law. They found that, in medical-marijuana states, the average doctor prescribed 265 fewer doses of antidepressants each year, 486 fewer doses of seizure medication, 541 fewer anti-nausea doses and 562 fewer doses of anti-anxiety medication. But most strikingly, the typical physician in a medical-marijuana state prescribed 1,826 fewer doses of painkillers in a given year. Estimating the cost savings to Medicare from the decreased prescribing, [the study] found that about $165 million was saved in the 17 medical marijuana states in 2013. The estimated annual Medicare prescription savings would be nearly half a billion dollars if all 50 states were to implement similar programs.