Chronobiology of mood disorders

Objective: As part of a series of papers examining chronobiology ['Getting depression clinical guidelines right: time for change?' Kuiper et al. Acta Psychiatr Scand 2013; 128(Suppl. 444): 24-30; and 'Manipulating melatonin in managing mood' Boyce & Hopwood. ActaPsychiatrScand 2013; 128(Suppl. 444): 16-23], in this article, we review and synthesise the extant literature pertaining to the chronobiology of depression and provide a preliminary model for understanding the neural systems involved. Method: A selective literature search was conducted using search engines such as MEDLINE/PubMed, combining terms associated with chronobiology and mood disorders. Results: We propose that understanding of sleep-wake function and mood can be enhanced by simultaneously considering the circadian system, the sleep homoeostat and the core stress system, all of which are likely to be simultaneously disrupted in major mood disorders. This integrative approach is likely to allow flexible modelling of a much broader range of mood disorder presentations and phenomenology. Conclusion: A preliminary multifaceted model is presented, which will require further development and testing. Future depression research should aim to examine multiple systems concurrently in order to derive a more sophisticated understanding of the underlying neurobiology.