People should stay away from cigarettes if they want to avoid chronic back pain.

Researchers from Northwestern University found that smokers are three times more likely than nonsmokers to develop chronic back pain, and dropping the habit may cut the risk of developing this often debilitating condition.

"Smoking affects the brain," Bogdan Petre, lead author of the study and a technical scientist at Northwestern University Feinberg School of Medicine, said in a statement. "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."

The results come from a longitudinal observational study of 160 adults with new cases of back pain. At five different times throughout the course of a year they were given MRI brain scans and were asked to rate the intensity of their back pain and fill out a questionnaire which asked about smoking status and other health issues. Thirty-five healthy control participants and 32 participants with chronic back pain were similarly monitored.

Petre and his colleagues analyzed MRI activity between two brain areas (nucleus accumbens and medial prefrontal cortex, NAc-mPFC), which are involved in addictive behavior, and motivated learning. This circuitry is critical in development of chronic pain, the scientists found.

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 with pain chronification, the findings hint at a potentially more general link between addiction and pain.

"That circuit was very strong and active in the brains of smokers," Petre said. "But we saw a dramatic drop in this circuit's activity in smokers who -- of their own will -- quit smoking during the study, so when they stopped smoking, their vulnerably to chronic pain also decreased."

This is the first evidence to link smoking and chronic pain with the part of the brain associated with addiction and reward.

The findings are detailed in the online journal Human Brain Mapping.