BDNF and bipolar disorder: Several genes (Brain-derived neurotrophic factor, BDNF; Catecol-O-Metiltransferase, COMT; CACNA1C; Dopamine and GABA receptors) have been identified that may be involved in the development of bipolar disorder, including those that regulate neurotransmitters such as serotonin and dopamine, and those that influence circadian rhythms (sleep-wake cycles).