* Changes 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.
* The possibility that the relationship between depression and smoking is bidirectional: depression increases the risk of smoking, and chronic smoking increases a person's susceptibility to depression. The same genes may contribute to both. For example, decreased activity of dopamine -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.
*Improve precision 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.
* Use longitudinal studies toprovide more complete information on the relative risk, incidence, and course of smoking and various mental disorders.
* Explore the 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.
* Discover 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.
* Assure adequate sample sizes in smoking cessation trials, and 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.