Association of alpha4beta2 nicotinic receptor and heavy smoking in schizophrenia.
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INTRODUCTION: Previously we suggested that the CHRNA7 polymorphism in nicotinic receptor genes, in particular the D15S1360 in CHRNA7, is associated with smoking in schizophrenia. Schizophrenia patients are usually heavy smokers. In this study we hypothesized that high-affinity nicotinic receptors are associated with smoking in such patients. OBJECTIVE: To investigate the role of alpha4 (Ch 20) and beta2 (Ch 1) genes in conferring a risk for smoking and for smoking a large number of cigarettes daily in subjects with schizophrenia. METHODS: Our study sample consisted of 241 white European schizophrenia patients (157 smokers and 84 nonsmokers) from the Toronto area. Current smoking status was assessed by the medical history. We investigated 4 markers located in the CHRNA4 gene and 3 markers located in the CHRNB2 gene. RESULTS: There was no difference in age or ethnicity between the 2 groups and the population was not stratified (lambda=0.4527). We found a significant association between the CHRNA4 rs3746372 allele 1 and a large number of cigarettes smoked daily (p=0.0203). The intragenic interaction between rs3787116 and rs3746372 (p = 0.0050) in CHRNA4 showed a significant interaction for the number of cigarettes smoked. CONCLUSION: Although our findings suggest an association between rs3746372 allele 1 and heavy smoking, further study is warranted to investigate the relation between smoking and high-affinity nicotinic receptor genes in schizophrenia.