Sleep-wake cycle and melatonin rhythms in adolescents and young adults with mood disorders: Comparison of unipolar and bipolar phenotypes

This study evaluated the potential of circadian measures as early markers of mood disorders subtypes. Patients with bipolar disorders had significantly lower levels and later onset of melatonin secretion than those with unipolar depression. Furthermore, abnormal phase angles between sleep, melatonin and temperature were found in several patients.