Circadian Genes, Rhythms and the Biology of Mood Disorders

Circadian Genes, Rhythms and the Biology of Mood Disorders: "Indeed some of the major hallmarks of diseases like major depressive disorder (MDD) and bipolar disorder (BPD) are abnormal sleep/wake, appetite, and social rhythms (Boivin, 2000; Bunney and Bunney, 2000; Lenox et al., 2002; Grandin et al., 2006). Depression symptoms are also diurnal with the most severe symptoms occurring typically in the morning (Rusting and Larsen, 1998), and depression is more prevalent in areas of the world that receive little sunlight for extended periods of time (Booker et al., 1991). In addition, one of the most common mood disorders, affecting some 2–5% of the population in temperate climates, is seasonal affective disorder (SAD), a syndrome where depressive symptoms occur only in the winter months when there are shorter days and a later dawn (Lam and Levitan, 2000; Magnusson and Boivin, 2003). Thus, it has long been hypothesized that abnormalities in the molecular clock underlie the development of these disorders. "

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