Relationship between nicotine dependence and the endophenotype-related trait of cognitive function but not acoustic startle reponses in Japanese patients with schizophrenia

Objectives: We investigated whether nicotine dependence affects these endophenotypes in Japanese schizophrenia patients and whether alpha4 and beta2 subunits of neuronal nicotinic acetylcholine receptor genes (alpha4 subunit of the nAChR gene (CHRNA4)/beta2 subunit of the nAChR gene (CHRNB2)) were associated with nicotine dependence in patients (n = 100) and healthy controls (n = 107). Methods: First, in patients, we evaluated cognitive function, using the Brief Assessment of Cognition in Schizophrenia, and acoustic startle responses. Second, we evaluated the severity of nicotine dependence, using the Tobacco Dependence Screener, the Fagerström Test for Nicotine Dependence, and the Brinkman index in current smokers in both groups. Third, we evaluated the relationship between acoustic startle responses, cognitive function, and severity of nicotine dependence. Finally, using 12 tagging single-nucleotide polymorphisms in each the CHRNA4/CHRNB2, we used multiple linear regression analysis to examine the association between nicotine dependence measures and each selected single-nucleotide polymorphism. Results: The presence and severity of nicotine dependence were associated with verbal memory and executive function in schizophrenia patients. However, nicotine dependence was not correlated with any acoustic startle response. In addition, rs755203 and rs1044397 in CHRNA4 were associated with nicotine dependence in healthy controls. Conclusions Nicotine dependence might influence the level of verbal memory and executive function in schizophrenia patients. In addition, rs755203 and rs1044397 in CHRNA4 might play a role in the pathophysiology of nicotine dependence in healthy controls in the Japanese population.