Nearly half of all cigarettes sold in the United States are sold to people with mental illness, and men and women with mental disorders are twice as likely as the general population to smoke. A recent NIDA-supported epidemiological analysis reveals relationships between psychiatric disorders and smoking that have important implications for public health. The findings suggest that treating psychiatric illness can contribute to reductions in smoking intensity and nicotine addiction, and that addressing smoking during substance abuse treatment is vital to counter an increased risk for nicotine addiction that may accompany recovery.

Dr. Naomi Breslau, at Michigan State University in East Lansing, used data from the Tobacco Supplement to the National Comorbidity Survey (NCS) to study the relationships between the temporal onset of psychiatric disorders, psychiatric symptoms, and smoking. The NCS, mandated by Congress to assess the prevalence of psychiatric disorders in the United States, surveyed a representative sample of the national population between 1990 and 1992, eliciting information about the onset of psychiatric disorders¡ªas defined by the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, 3rd Edition Revised (DSM-III-R)¡ªand the time course of their symptoms. Disorders included in the NCS are major depression, dysthymia (similar to clinical depression, but with longer-lasting and milder symptoms), agoraphobia, generalized anxiety disorder, simple and social phobias, panic disorder, posttraumatic stress disorder, and alcohol or drug abuse or addiction. The NCS Tobacco Supplement asked respondents whether they smoked, when they began smoking daily, at what age they experienced symptoms matching DSM criteria for nicotine dependence, and whether they had stopped smoking regularly a year or more before they took part in the survey.

Researchers found that active psychiatric disorders, with the exception of agoraphobia and panic disorder, were associated with increased risk of transition to daily smoking. In contrast, past disorders (those that had been inactive for a year or more) generally did not predict transition to daily smoking. Researchers also found an increased risk of transition to nicotine addiction associated with a wide range of active disorders, but only four past disorders. Risks are presented as odds ratios; a relative risk of 2.0 indicates twice the likelihood.

Analyzing the responses from 4,414 survey participants, Dr. Breslau found that:

• Men and women with histories of substance abuse, major depression, and most anxiety disorders reported increased rates of transition to daily smoking, but only during periods when they were experiencing symptoms. When their illnesses had been asymptomatic for a year or more, they became daily smokers at rates no higher than respondents who never experienced psychiatric illness;
• Substance abuse and major depression predicted transitions from voluntary smoking to nicotine addiction when actively symptomatic (the association was borderline for drug, as opposed to alcohol, abuse). In the case of substance abuse, this relationship became markedly stronger when the problems had remitted for at least a year;
• Most anxiety disorders increased risk for nicotine addiction when symptomatic. For individuals with simple phobia or panic disorder, these risks multiplied during periods of remission. For those with posttraumatic stress disorder, the risk reverted to baseline when symptoms had been absent for a year; and
• None of the psychiatric disorders studied affected respondents' chances of successfully quitting smoking, either when active or when remitted.

"We found that the majority of the psychiatric disorders, when active, predicted the onset of daily smoking," Dr. Breslau says. "Respondents with one active disorder were 1.3 times as likely, and those with four or more active disorders were 2.2 times as likely to begin daily smoking as those with no active disorders. This suggests that early treatment may be able to prevent patients who are not currently daily smokers from progressing to that status."

"Similarly," Dr. Breslau says, "most disorders¡ªwhen active¡ªpredicted that smokers would progress from daily smoking to nicotine addiction. In this transition from one stage of smoking to another, daily smokers with one active disorder were on average 1.8 times as likely as those with no active disorder to develop addiction, and the odds of developing nicotine addiction increased with the number of active disorders. This suggests that successful control of psychiatric symptoms before smokers become addicted can prevent them from making that transition."

Substance abuse, however, is an important exception to this general observation. Respondents with past but not active alcohol and drug abuse disorders had risk ratios two to three times as high as respondents with current active disorders involving these substances. "This association suggests that cessation of substance abuse may induce greater smoking intensity. In treatment for substance use disorders it is important to be conscious of smoking behavior, to guard against the possibility that a person in treatment for one damaging condition might increase the danger posed by another. Treatment should assist patients who are abusing alcohol or drugs and who smoke to quit both," Dr. Breslau says.

When Dr. Breslau looked for a relationship between mental disorders and quitting smoking, she found that neither active nor remitted disorders made respondents more or less likely to quit smoking successfully during the year preceding the survey.

"The relationship between tobacco use and comorbid psychiatric disorders is complex," says Dr. Kevin Conway of NIDA's Division of Epidemiology, Services and Prevention Research. "While we see variations across the range of disorders included in the comorbidity survey, the consistent pattern in this study emphasizes the importance of active expression of psychiatric disorders¡ªnot simply a history of the disorder¡ªin relation to smoking stages."