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Updated: Apr 21, 2026

Human Circadian Phenotyping and Diurnal Performance Testing in the Real World
Published on: April 7, 2020
Intra- and inter-individual variability of longitudinal daytime melatonin secretion patterns in depressed and
Maria E J Bouwmans1, Elisabeth H Bos, Sanne H Booij
1Interdisciplinary Center of Psychopathology and Emotion Regulation, University Medical Center Groningen, University of Groningen , Groningen , The Netherlands and.
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.
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