Smoking and Mental Illness: Which One’s the Chicken?

Ron, a 55-year-old man, has not been doing very well lately. First, one of his lungs collapsed, and then X-rays suggested that he might have a malignant growth in his lungs. In spite of these health scares, though, he hasn’t managed to give up his three-pack-a-day cigarette smoking habit. There is little doubt that Ron is nicotine dependent.

Heavy smokers like Ron are not just at risk for the usual smoking-related diseases like cancer, emphysema, and heart disease. They also experience poorer mental health than do nonsmokers and even moderate smokers.

So, in any event, suggests a study conducted in Germany (a country considerably behind the United States in foregoing smoking) and reported in the September American Journal of Psychiatry. The investigation was headed by Norbert Schmitz, Ph.D., of the Clinic for Psychosomatic Medicine and Psychotherapy of the Heinrich-Heine-University in Duesseldorf.

From 1997 to 1999, the German Ministry of Science surveyed a representative sample of individuals from the noninstitutionalized population of Germany to learn more about the physical and mental health of Germans.

The survey was called the German National Health Interview and Examination Survey. It included a physical examination by a physician, a self-administered questionnaire about physical and mental health, and a psychiatric interview with the Composite International Diagnostic Interview for DSM-IV disorders. Some 4,000 Germans participated.

Schmitz and his coworkers then used data from all 4,000 Germans to determine the prevalence of nicotine dependence. They found that while some 36 percent of the 4,000 subjects smoked, only about 9 percent of them were truly nicotine-dependent according to DSM-IV criteria. Nicotine-dependent smokers smoked, on average, 20 cigarettes a day, whereas smokers not dependent on nicotine smoked, on average, 14 cigarettes a day.

The investigators then used data from 3,000 of the 4,000 subjects to learn whether there was a mental health difference between those who were nicotine dependent and those who were not. They found that even when they took sociodemographic factors into consideration, nicotine-dependent subjects reported a poorer quality of life than did subjects who did not smoke and subjects who smoked but were not nicotine dependent.

In other words, there was a highly statistically significant difference on dimensions having to do with mental health and a statistically significant difference between the nicotine-dependent subjects and the other subjects on dimensions having to do with other areas of health.

The researchers then looked to see whether there were any differences between nicotine-dependent subjects and nonsmokers and between nicotine-dependent subjects and non-nicotine-dependent smokers as far as anxiety disorders, depressive disorders, somatoform disorders, and substance abuse other than nicotine dependence were concerned. The researchers found that more than half of nicotine-dependent subjects reported at least one of these types of mental disorders during the preceding year, compared with only a fourth of the nonsmokers and non-nicotine-dependent smokers.

For example, anxiety disorders were more than twice as common among the nicotine-dependent smokers as among the nonsmokers and non-nicotine-dependent smokers—28 percent versus 12 percent and 14 percent, respectively. Depressive disorders were about twice as common among the nicotine-dependent group as among the other two groups—24 percent versus 11 percent and 11 percent, respectively.

The abuse of substances other than nicotine was also considerably higher in the nicotine-dependent smokers than in the nonsmokers and non-nicotine-dependent smokers—14 percent versus 1 percent and 4 percent, respectively.

Still unanswered, however, is whether heavy smoking leads to poor mental health or whether poor mental health leads to heavy smoking. The researchers speculated that a third possible scenario is that both occur. In other words, people who have trouble coping with stress, anxiety, and depression might be vulnerable to nicotine dependency, and then once they become dependent on it, they might try to stop smoking and not succeed, and that failure in turn might make them even more anxious and depressed than they were initially.

The study, “Disabilities, Quality of Life, and Mental Disorders Associated With Smoking and Nicotine Dependence,” is posted on the Web at http://ajp.psychiatryonline.org/cgi/content/full/160/9/1670?. ▪

Am J Psychiatry 2003 160 1670