Molecular Psychiatry
A notable feature of bipolar disorder is the photoperiod driven, seasonal occurrence of symptoms and episodes mediated by circadian systems, with mania occurring more frequently in the spring and autumn at times of rapid rate of change in photoperiod, and depression being more prevalent in the winter when photoperiod is attenuated.
Such mechanisms encompass targets of lithium involved in insulin signaling (the phosphatidylinositol cycle, GSK3β and Akt), clock genes (CLOCK and BMAL1), targets of psychiatric and metabolic medications (mTOR and AMPK) and hormonal signaling (melatonin and cortisol).