Circadian neurogenetics of mood disorders

Mood state alterations are often accompanied by disruptions of daily rhythms of physiology. Circadian rhythms of physiology are controlled by a central clock harbored in the suprachiasmatic nucleus (SCN), which is functionally dependent on the rhythmic expression of several clock genes. The molecular clockwork has been identified in other extra-SCN brain regions, some of which are implicated in the regulation of motivational and emotional states, although their specific circadian role is not fully known. In mood disorders, alterations of the molecular clock have been reported. Thus, functional expression of circadian genes in the brain is compromised in mood diseases. In the present review, we describe the current evidence that implicates the clock gene alterations as an important factor in the development of mood-related disorders. Furthermore, we describe the possible role of other brain clocks, beyond the SCN, in the circadian control of mood. The comprehension of the circadian neural and genetic mechanisms underlying mood alterations might guide towards the identification of optimal drug and non-drug therapies for the cure of depression and other mood disorders.