Association between COMT Val158Met and Tobacco Smoking among Subjects with Schizophrenia and Bipolar Disorder: A Pilot Study

Mentally ill patients are frequently tobacco smokers. This pilot study determined the association between the Catechol-O-Methyltransferase (COMT) Val158Met (rs4680) variants and smoking in patients with schizophrenia and bipolar disorder. The subjects were classified into current, former and neversmokers, and subdivided according to race gender and the genotype. The number of cigarettes smoked per day was used as the major parameter to assess their smoking behavior. Female schizophrenic smokers with the Met allele smoked significantly more cigarettes per day than males with the Val/ Val genotype and schizophrenia. This significance was detected among African American, but not Caucasian patients with schizophrenia. Especially in female African Americans, the Met allele carriers smoked significantly more cigarettes per day than the Val/Val carriers. No significant association between the COMT genotypes and smoking status was found in patients with schizophrenia or bipolar disorder. In addition, no significant genotype and sex-related differences were found in Caucasians with schizophrenia or bipolar disorder. The results demonstrate that the COMT Met allele affects the number of cigarettes smoked per day, but this effect was sex, ethnic, and mental diagnosis-specific.