Inheritance of a defect in a neuronal mechanism that regulates response to auditory stimuli was studied in nine families with multiple cases of schizophrenia. The defect, a decrease in the normal inhibition of the P50 auditoryevoked response to the second of paired stimuli, is associated with attentional disturbances in schizophrenia. Decreased P50 inhibition occurs not only in most schizophrenics, but also in many of their nonschizophrenic relatives, in a distribution consistent with inherited vulnerability for the illness. Neurobiological investigations in both humans and animal models indicated that decreased function of the ␣7-nicotinic cholinergic receptor could underlie the physiological defect. In the present study, a genome-wide linkage analysis, assuming autosomal dominant transmission, showed that the defect is linked [maximum logarithm of the odds (lod) score ‫؍‬ 5.3 with zero recombination] to a dinucleotide polymorphism at chromosome 15q13-14, the site of the ␣7-nicotinic receptor. Despite many schizophrenics' extremely heavy nicotine use, nicotinic receptors were not previously thought to be involved in schizophrenia. The linkage data thus provide unique new evidence that the ␣7-nicotinic receptor gene may be responsible for the inheritance of a pathophysiological aspect of the illness.

The National Institute of Mental Health (NIMH) convened a meeting in September 2005 to review tobacco use and dependence and smoking cessation among those with mental disorders, especially individuals with anxiety disorders, depression, or schizophrenia. Smoking rates are exceptionally high among these individuals and contribute to the high rates of medical morbidity and mortality in these individuals. Numerous biological, psychological, and social factors may explain these high smoking rates, including the lack of smoking cessation treatment in mental health settings. Historically, "self-medication" and "individual rights" have been concerns used to rationalize allowing ongoing tobacco use and limited smoking cessation efforts in many mental health treatment settings. Although research has shown that tobacco use can reduce or ameliorate certain psychiatric symptoms, overreliance on the self-medication hypothesis to explain the high rates of tobacco use in psychiatric populations may result in inadequate attention to other potential explanations for this addictive behavior among those with mental disorders. A more complete understanding of nicotine and tobacco use in psychiatric patients also can lead to new psychiatric treatments and a better understanding of mental illness. Greater collaboration between mental health researchers and nicotine and tobacco researchers is needed to better understand and develop new treatments for cooccurring nicotine dependence and mental illness. Despite an accumulating literature for some specific psychiatric disorders and tobacco use and cessation, many unstudied research questions remain and are a focus and an emphasis of this review.