SALIVARY AND PLASMA MEASURES OF DIM LIGHT MELATONIN ONSET (DLMO) IN PATIENTS WITH RAPID-CYCLING BIPOLAR DISORDER

A number of researchers have suggested that the phase (timing) of circ adian rhythms in depressed patients is abnormal. Longitudinal studies could help to elucidate the relationship between circadian phase and m ood, Such studies would be facilitated by the development of a noninva sive method for measuring circadian phase. In normal volunteers, the c oncentration of salivary melatonin measurements has been shown to be s ignificantly correlated with those obtained in plasma; however, it is unknown whether salivary melatonin measurements can reliably detect th e unmasked time of onset of nocturnal melatonin secretion (a measure o f circadian phase), In addition, the relationship between salivary and plasma melatonin measurements in medicated psychiatric patients is un known. We measured plasma and salivary melatonin simultaneously in a s ample of 12 medicated patients with rapid cycling bipolar disorder, Th e intraclass correlation coefficient between plasma and salivary measu res of the dim light melatonin onset (DLMO) was 0.93. We therefore con clude that salivary melatonin can be used to determine the time of the DLMO in this population.