Opioid drugs* like oxycodone, hydrocodone, methadone, and heroin caused over 28,000 deaths in the United States in 2014, more than any earlier year on record, according to the Centers for Disease Control and Prevention (CDC). It was estimated in 2012 that about 2.1 million Americans suffered substance abuse disorders related to prescribed opioids and another half million were addicted to heroin. From 1999 to 2014, the number of prescription opioids sold in the United States more than quadrupled, as did related deaths, “yet there has not been an overall change in the amount of pain that Americans report.” Chronic pain affects 11.2% of US adults (about 100 million), with 3-4% of those receiving long-term opioid therapy at an annual cost of $635 billion.

However, in those states that allow medical use of cannabis (Cannabis sativa, Cannabaceae), opioid-related mortality has declined significantly since enactment of such laws. The use…