[Melatonin. Chronobiologic peripheral endocrine index in depressive states].

The chronobiological studies with melatonin constitute valid arguments to consider melatonin as a peripheral index of depressive disorders. In a group of patients with major depression, we reported a lowering of melatonin nocturnal plasma levels, associated with cortisol hypersecretion. A similar lowering of melatonin was observed in a group of patients with cluster headaches, but without quantitative modification of cortisol secretion. Other studies are necessary in order to determine wether melatonin may be considered as a "state marker" of depression itself or a marker of the genetic vulnerability to depression.