MN blood groups and bipolar disorder: Evidence of genotypic association and Hardy-Weinberg disequilibrium

Background: MN blood groups have been studied in the past as a genetic marker of bipolar disorder (BD). Several previous studies reported art association of the illness with lower frequency of blood group NN, Methods: We analyzed distribution of MN blood groups in a sample of 174 patients with ED, 176 with unipolar depression, 98 with schizophrenia, and 331 healthy controls. In addition, we tested whether the inferred genotypes conform to Hardy-Weinberg equilibrium (HWE), Results: The frequency of NN phenotype was significantly lower among the bipolar patients than in any of the other three groups (p < .001), The genotype frequencies in the ED group deviated significantly from those expected under HWE (p < .01), Conclusions: These results suggest a possible locus on chromosome 4 (4q28-q31.1) associated with generic susceptibility to bipolar illness. (C) 1998 Society of Biological Psychiatry.