Daily smokers have twice the risk for major depression compared to people who have a history of smoking on an occassional basis, according to a Henry Ford Health System study.
In addition, researchers found that not only may smoking lead to depression, but depression may lead to increased smoking. The study revealed that in young adults who smoke and have history of major depression, their risk of becoming daily smokers is three times more likely. The progession to daily smoking typically begins in adolescence.
The study, published in the February issue of Archives of General Psychiatry, is the first-of-its-kind to demonstrate the influence of major depression on increased smoking. The study tracked 1,000 young adults ages 21 to 30 over a period of five years in southeastern Michigan. A daily smoker is defined as a person who smokes daily for one or more months.
Interestingly, no conclusive data showed that major depression played a role in the initiation of smoking, nor did it show smokers with depression have a harder time quitting, said Naomi Breslau, Ph.D., principal investigator and director of research for the Department of Behavioral Services at Henry Ford Health System. She offers several possible explanations for the relationship between depression and smoking.
"Smokers who have depression tend to see their smoking become a daily habit, and it may be because they use nicotine to medicate their depressed mood," Dr. Breslau said. An addiction to nicotine may be especially powerful in depressed smokers because of the substance's mood-altering characteristics.
The Henry Ford data also revealed that smokers are significantly more at risk of major depression. But does smoking cause depression" There may be neurobiologic evidence that nicotine and other smoke substances play a role in causing depression, but additional research is needed to support this, according to Dr. Breslau.
"We may find that factors predispose people to both depression and smoking. Social environment and personality may be the common causes. One study suggests that the relationship results solely from genetic predisposition. Future research is needed to determine what, if any, are the common causes of both," Dr. Breslau said.
NOTE: A copy of the study is available by request. Please call Meredith Meyer at (313) 876-2882.