Smoking is a pain in the back.

• Position: Nicotine

If you want to avoid chronic back pain, put out the cigarette. A study by Northwestern University, Chicago, Ill., has found that smokers are three times more likely than nonsmokers to develop chronic back pain, and dropping the habit may cut your chances of developing this often debilitating condition.

"Smoking affects the brain," points out Bogdan Petre, lead author of the study and a technical scientist at the School of Medicine. "We found that it affects the way the brain responds to back pain and seems to make individuals less resilient to an episode of pain."

This is the first evidence to link smoking and chronic pain with the part of the brain associated with addiction and reward. These two regions of the brain "talk" to one another and scientists discovered that the strength of that connection helps determine who will become a chronic pain patient. By showing how a part of the brain involved in motivated learning allows tobacco addiction to interface...