Schizophrenia, smoking and the alpha 7 nicotinic receptor gene

Smoking occurs at higher rates than other types of substance abuse or dependence amongst individuals with schizophrenia. The frequency of smoking for schizophrenia is higher than for persons in the normal population and higher than the rate for psychiatric patients in general. This observation extends across many countries and cultures (e.g., the United States, Ireland, Chile, and others). The prevalence of smoking among schizophrenics is between 70-80%, rising higher for inpatient status, al-most three times the prevalence found in a normal population. Such increased prevalence may be due to selfmedication as nicotine transiently improves sensory gating, thought to be one of the major cognitive deficiencies in schizophrenia. Defects in sensory gating as indexed by the P50 evoked potential have been linked to a dinucleotide polymorphism at 15q13-q14 with a lod score of 5.3 with zero recombination [Freedman et al., 1997]. The objective of this study was to explore the relationship between smoking behaviour and D15S1360, a dinucleotide repeat 120 Kbp from exon 1 of CHRNA7, in a sample of 102 probands meeting narrow criteria (DSM-IV schizophrenia or schizoaffective depression). No association between D15S1360 and smoking behaviour was found. Implications of this finding are discussed.