Childhood Attention Deficit in the Patients with Bipolar Disorder and CHRNA7 Gene Polymorphisms

Jeong, Seong Hoon; Kim, Eui Joong; Lee, Kyu Young; Koo, Young Jin; Song, Joo Yun; Song, Hye Jin; Yi, Ju Eun; Joo, Eun Jeong

Abstract

OBJECTIVE
Patients with bipolar disorder have attention deficit during even euthymic status. Bipolar disorder patients showed more childhood attention deficit and other ADHD like feature. Alpha 7 nicotinic receptor (CHRNA7) gene has been known to play roles in attention and sensory gating, and association between CHRNA7 gene and bipolar disorder has been reported. Therefore, we investigated a possible association between childhood attention deficit of bipolar disorder and CHRNA7 gene polymorphisms.
METHODS
We included 122 patients with bipolar disorder (89 subjects of bipolar disorder type I, 33 subjects of bipolar disorder type II). Childhood attention deficit was measured by Wender Utah Rating Scale (WURS). Factor analysis was done for WURS to extract inattention factor from childhood ADHD like feature. Three factors were extracted: Impulsivity, Inattention, and Mood instability. All subjects were ethnically Korean. Genotyping was done for three intronic Single Nucleotide Polymorphism (SNPs) of CHRNA7 gene: rs2337506 (A/G), rs6494223 (C/T), and rs12916879 (A/G). Analysis of association was done by UNPHASED version 3.1.4, a free software for genetic statistics.
RESULTS
Genetic association tests found no association between factor score of inattention and any SNP or combination of SNPs of CHRNA7. Positive association between WURS total score and SNP rs6494223 (p=0.043), factor score of impulsivity and SNP rs2337506 (p=0.038) as well as SNP rs6494223 (p=0.043) was revealed. These positive associations were survived after 1,000 permutation tests. Combination of SNPs association tests performed for total WURS and factor scores could not find any significant association.
CONCLUSION
We could not find association between CHRNA7 gene and childhood attention deficit in bipolar disorder. However, we found CHRNA7 gene involved in childhood impulsivity of bipolar disorder, another ADHD like feature. Further studies with larger sample and denser polymorphisms are necessary to clarify genetic role of CHRNA7 in attention and impulsivity of bipolar disorder.