Background: Mood swings, or mood variability, are associated with negative mental health outcomes. Since adolescence is a time when mood disorder onset peaks, mood variability during this time is of significant interest. Understanding biological factors that might affect mood variability, such as sleep and structural brain development, could elucidate the mechanisms underlying mood disorders.
Methods: Data from the longitudinal Leiden Self-Concept study (N=171) over 5 timepoints was used to study the association between sleep, brain structure, and mood variability in healthy adolescents aged 11-21 at baseline in this pre-registered study. Sleep was measured both objectively, using actigraphy, as well as subjectively, using a daily diary self-report. Negative mood variability was defined as day-to-day negative mood swings over a period of 5 days after an MRI scan.
Results: It was found that negative mood variability peaked in mid-adolescence, and average negative mood showed a similar pattern. Sleep duration (subjective and objective) generally decreased throughout adolescence. Mood variability was not associated with sleep, but average negative mood was associated with higher self-reported lower energy. In addition, higher thickness in the dorsolateral prefrontal cortex (dlPFC) compared to same-age peers, suggesting a delayed thinning process, was associated with higher negative mood variability in early and mid-adolescence. Lastly, higher mood variability preceded higher levels of anxiety and depression, as well as current anxiety and depression. Conclusions: Together, this study provides an insight into the development of mood variability and its association with brain structure.