Association of nicotinamide-N-methyltransferase (NNMT) gene rs694539 variant with bipolar disorder

•Association of the rs694539 variant of NNMT gene with bipolar disorder was shown.•Association is female gender specific.•A PCR-RFLP method was developed.

Here we report the association of the rs694539 variant of nicotinamide-N-methyltransferase gene with bipolar disorder in a case–control study of 95 bipolar disorder patients and 201 healthy controls (χ2 = 13.382, P = 0.001). With the polymerase chain reaction restriction fragment length polymorphism method we developed we were able to show the association for the first time. This new finding may provide evidence to understand the mechanism of the disease.