An anonymous reader writes: Narcotic painkillers aren't one of the biggest killers in the U.S., but overdoses do claim over 15,000 lives per year and send hundreds of thousands to the emergency room. Because of this, it's interesting that a new study (abstract) has found states that allow the use of medical marijuana have seen a dramatic reduction in opioid overdose fatalities. "Previous studies hint at why marijuana use might help reduce reliance on opioid painkillers. Many drugs with abuse potential such as nicotine and opiates, as well as marijuana, pump up the brain's dopamine levels, which can induce feelings of euphoria. The biological reasons that people might use marijuana instead of opioids aren't exactly clear, because marijuana doesn't replace the pain relief of opiates. However, it does seem to distract from the pain by making it less bothersome." This research comes at a time when the country is furiously debating the costs and benefits of marijuana use, and opponents of the idea are paying researchers to paint it in an unfavorable light.