Family-based association studies of bipolar disorder with candidate genes involved in dopamine neurotransmission: DBH, DAT1, COMT, DRD2, DRD3 and DRD5

The dopaminergic system has been implicated in the aetiology of mood disord ers. We conducted family-based association studies for polymorphisms at thr ee genes involved in the metabolism of dopamine: dopamine transporter (DAT1 ), dopamine-p-hydroxylase (DBH) and catechol-O-methyl transferase (COMT); a nd three dopamine receptors: DRD2, DRD3 and DRD5. We used a sample of 122 p arent-offspring trios of British Caucasian origin where the proband had bip olar disorder I (BPI), and analysed the results with the transmission/diseq uilibrium test (TDT) which is robust to hidden population stratification. N o statistically significant differences were found between transmitted and not transmitted alleles for any of the polymorphisms studied.