People who have experienced depression are especially vulnerable to nicotine addiction and have a particularly hard time quitting smoking, according to new research that suggests that many people use smoking as a form of "self-medication" against anxiety and pain.
The findings are considered important because of the dire health consequences of smoking and the difficulties of smoking cessation. The research suggests that for some people, it may be unrealistic to expect to quit smoking without first being treated for depression.
"This is probably the best evidence yet that certain people are more susceptible to drug addiction than others," said Dr. Alexander H. Glassman of Columbia University, an author of one of two studies to be published today in the Journal of the American Medical Association.
The reasons for what Glassman called this "chronic and pernicious interrelationship" are not clear.
Because nicotine is a stimulant, researchers suspect that some smokers use it to fend off the anxiety and discontent of depression. Over time, those feelings may come to trigger cravings for nicotine because it has alleviated them in the past.
Similarly, the anxiety that accompanies nicotine withdrawal may be more severe among depressed ex-smokers and more likely to drive them back to cigarettes. Researchers say that some depression-prone smokers have been driven back into depression by an attempt to quit.
Another possible explanation is that some factors, such as low self-esteem, may predispose people to both depression and smoking.
Or, there may be a genetic factor that can lead to both depression and smoking, some researchers suggest.