An analysis of 160 people found that smokers are three times more likely than nonsmokers to develop chronic back pain. Possible reason: Smokers have a stronger connection between two brain regions that play a role in addictive behavior and chronic pain. Good news: Study participants who quit smoking showed a drop in this brain circuit activity, decreasing their vulnerability to chronic pain.

A. Vania Apkarian, PhD, professor of physiology, Northwestern University Feinberg School of Medicine, Chicago.