Intra- and inter-individual variability of longitudinal daytime melatonin secretion patterns in depressed and non-depressed individuals

Abstract

Disrupted melatonin secretion is regarded as a link between circadian rhythm and major depression, but results have been contradictory. We hypothesize that this might be due to averaging across individuals and too short measurements periods. In this study, pair-matched depressed and non-depressed individuals sampled their saliva three times a day, 30 days, in their natural environment. The depressed group showed significantly more variance and higher melatonin levels (p < 0.05). Substantial interindividual heterogeneity and day-to-day variability was found. The individual time-series approach allowed us to reveal this variability. Important information remains unnoticed when analyzing melatonin only at the group level.

• Individual differences
• longitudinal studies
• major depressive disorder
• melatonin
• saliva

Declaration of Interest

The authors declare that they have no conflicts of interest. This study was supported by a VICI grant entitled Deconstructing Depression (no: 91812607) received by Prof. Dr. Peter de Jonge from the Netherlands Organization for Scientific Research (NWO-ZonMW). S.H. Booij, E.H. Bos, A.J. Oldehinkel, P. de Jonge designed the study and wrote the protocol. M. van Faassen analyzed the saliva samples. M.E.J. Bouwmans and E.H. Bos undertook the statistical analyses, and M.E.J. Bouwmans wrote the first draft of the manuscript. All authors contributed to and have approved the final manuscript.