One thousand forty-nine participants were recruited: 249 with bipolar-I, 456 with bipolar-II, and 344 healthy controls. The genotypes of the ALDH2 and 5HT2A-A1438G polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis.
Logistic regression analysis showed a significant effect of the ALDH2 and the 5-HT2A-A1438G polymorphisms, and a significant interaction effect for the A/G genotypes of the 5-HT2A-A1438G polymorphism and the ALDH2*1*1 genotypes (p = 0.004) discriminated between bipolar-I patients and controls without bipolar disorder. These polymorphisms, however, were not associated with bipolar-II disorder.
The significant differences of age and gender between patients and controls limit the comparison, although statistical adjustments were made for them.
Our findings provide initial evidence that the ALDH2 and 5-HT2A genes interact in bipolar-I but not in bipolar-II disorder. Our findings suggest a unique genetic distinction between bipolar-I and bipolar-II.