Recommendations Urge Exploration of Causal Links, Treatment Research
• Science Update
Numerous biological, psychological, and social factors are likely to play a role in the high rates of smoking in people with psychiatric disorders, according to the report of an expert panel convened by the National Institute of Mental Health. The report reviews current literature and identifies research needed to clarify these factors and their interactions, and to improve treatment aimed at reducing the rates of illness and mortality from smoking in this population.
An analysis of data from the National Comorbidity Study (NCS), a nationally representative survey of psychiatric disorders in the United States, found that 41 percent of people with a psychiatric disorder smoke, about twice the rate (22.5 percent) seen in those without psychiatric diagnoses. People with psychiatric disorders consume 44.3 percent of all cigarettes smoked in this country. The high rate of smoking is an important factor in increased rates of physical illness and mortality in this group.
Despite the high smoking rates, studies of outpatient and hospital care of psychiatric patients reported that less than a quarter of outpatients with psychiatric diagnoses received counseling from their physicians aimed at smoking cessation, and in hospitals, only 1 percent of psychiatric inpatient smokers were assessed for smoking; none of the treatment plans for these patients addressed tobacco use.
The panel report suggests that the reasons for these low rates of assessment and treatment may include health professionals' acceptance of smoking by psychiatric patients as a matter of individual rights and as a means of self-medication aimed at relieving symptoms. The report goes on to note, however, that research on smoking in this population needs to explore other potential explanations for tobacco use besides self-medication.
In its review of current findings on co-occurring mental health disorders and smoking, the panel identified some provocative areas for continued research including the following:
- Alterations in the hypothalamic-pituitary-adrenal (HPA) axis, a system in the body involved in the response to stress, have been reported in post-traumatic stress disorder (PTSD). The HPA axis is also involved in the development of nicotine tolerance. The interplay of the HPA axis with stress and nicotine may help explain the increased smoking in those with PTSD and other anxiety disorders.
- Research suggests that the relationship between depression and smoking may be bidirectional: depression increases the risk of smoking, and chronic smoking increases a person's susceptibility to depression. The same genes may contribute to both. Decreased activity of dopamine, for example—a neurotransmitter that is central to the brain's reward system—is thought to be associated with depression; studies cited by the panel suggest that variants of genes that affect the level of dopamine function can influence the likelihood that someone with depression will smoke.
- As many as 70 to 85 percent of people with schizophrenia use tobacco. According to the panel, psychosocial factors are important in understanding the high rates of smoking people with schizophrenia. Limited education, poverty, unemployment, and peer influence increase smoking risk; the mental health treatment system, in which smoking is not only acceptable but sometimes condoned, is also a contributor.
- Nicotine has effects on some cognitive processes in people with schizophrenia and research has found that variants in the genes for nicotine receptors have been linked to deficits in these processes. The relationships between genes, environment, and smoking in this population are not fully understood.
The panel concluded by identifying issues that will be important for future research across these disorders:
- Better precision is needed in defining the specific psychiatric disorders of interest in a given study. "Depression," for example, is used in reference to a number of different conditions. Similarly, clearer definitions of smoking behavior and patterns and progression of use are needed.
- Longitudinal studies can provide more complete information on the relative risk, incidence, and course of smoking and various mental disorders.
- More focus is needed on exploring the potential causal links between tobacco use and psychiatric disorders, including possible genetic, neurobiological, psychological, or social factors. The extent to which smoking is used as a form of self-regulation needs to be explored.
- More information is needed on how smoking and other health related factors such as stress, obesity, and limited physical activity contribute to the illness and mortality seen in people with mental disorders.
- The report had a number of recommendations related to smoking cessation in this population. The report noted the need for adequate sample sizes in cessation trials; greater emphasis on adapting cessation treatment to various psychiatric populations and in different treatment settings; and research on how tobacco control polices affect psychiatric populations.
The report concludes by noting that research on smoking in this population can provide insights into the mechanisms that contribute to both tobacco dependence and psychiatric disorders.
William T. Riley, Ph.D., deputy director of NIMH's Division of AIDS and Health and Behavior Research, was a member of the group preparing this review, which included experts from university medical centers across the country.
Ziedonis, D., et al. Tobacco Use and Cessation in Psychiatric Disorders: National Institute of Mental Health Report. Nicotine & Tobacco Research, 2008;10:1-25.