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Preliminary evidence of an association between bipolar disorder in females and the catechol‐O‐methyltransferase gene

&NA; Catechol‐O‐methyltransferase (COMT) catalyses the methylation, and hence the inactivation, of catecholamines including the neurotransmitters dopamine and noradrenaline. There is evidence implicating COMT as a candidate gene for a number of neuropsychiatric conditions including bipolar disorder. A long recognized population variation in COMT activity exists and it has recently been established that variation in enzyme activity results from a polymorphic genetic variation within the COMT gene which can be readily assayed as a polymerase chain reaction (PCR)‐based restriction fragment length polymorphism (RFLP). A collection of 60 Irish bipolar I probands have been genotyped together with their parents. Tests comparing transmitted and non‐transmitted alleles provide no evidence that the polymorphism contributes to a susceptibility to bipolar disorder within the sample as a whole. However, amongst female bipolar I probands (n = 30) there was a tendency for the low‐activity allele of COMT to be preferentially transmitted. Furthermore, a re‐examination of an Irish case‐control sample resulted in a similar observation amongst female bipolar I sufferers and pooling the data sets strengthened the findings. Psychiatr Genet 8:221‐225 © 1998 Lippincott Williams & Wilkins.