Circadian and seasonal rhythms disturbances are prominent in patients with psychiatric disorders.
Properly timed and dosed light of specific spectral composition, stabilizes mood and sleep through serotonergic mechanisms and through input to the master circadian clock in the hypothalamus. Correctly administered, light can be used as an effective treatment for seasonal and non-seasonal depression, and for stabilizing the sleep-wake cycle. Blocking of evening blue light may provide a non-pharmacological anti-manic tool. Current developments use dynamic lighting built into somatic and psychiatric hospitals to maximize the beneficial effects of light.