In 2015, more Americans died from drug overdoses than from car accidents and gun homicides combined. That’s according to a startling interactive story published by The New York Times recently, which also noted that since 1990, drug-overdose deaths have increased by 500 percent.

A new study suggests unemployment might be one of the factors behind that dramatic rise. The paper, published by NBER last week, finds that as the unemployment rate increases by one percentage point in a given county, the opioid-death-rate rises by 3.6 percent, and emergency-room visits rise by 7 percent.

Rather than more people getting injured when jobs are scarce, the authors suspect that the increased use of painkillers is a “physical manifestation of mental-health problems that have long been known to rise during periods of economic decline.” Depression and pain are twin agonies, in other words: Not only does depression make people more sensitive to pain, they note, opioids have been shown to help relieve depressive symptoms.

This isn’t the only study that has linked joblessness with painkiller use. In another recent paper, the Princeton University labor economist Alan Krueger found that nearly half of “prime age” men who aren’t in the labor force take pain medication daily. And past studies have found that the unemployed are more likely to use illegal drugs than full-time workers.