Chronotype, depression, and circadian treatment strategies: Bridging the gap between epidemiology and clinical practice

This thesis investigates the relationship between circadian rhythms and depression. Circadian rhythms are natural cycles close to 24 hours that regulate sleep, wakefulness, and other functions in the human body. The research focuses on how these rhythms influence the course and treatment of depression.
The first part of this thesis examines the longitudinal association between chronotype (whether a person is a "morning person" or "night owl") and depression. It finds that while chronotype tends to remain consistent over time, shifts toward earlier sleep patterns are associated with improvements in depressive symptoms. Additionally, the results indicate that a shift towards an earlier chronotype over time is associated with increasing age, independent of severity of depressive symptoms.
The second part of the thesis examines how understanding circadian rhythms can enhance the (clinical) treatment of depression. Various circadian markers such as sleep patterns and mood changes throughout the day, are reviewed for their potential in predicting treatment outcomes. Moreover, actigraphy, a method that tracks sleep and activity levels, can identify patterns that may predict a positive response to treatment with combined chronotherapy.
In summary, the relationship between circadian rhythms and depression is complex and measurable on multiple levels. This thesis provides insights into the longitudinal association between chronotype and depressive symptoms, while also highlighting the potential of circadian markers in predicting treatment responses. Continued research in this field could lead to the integration of circadian rhythm assessments into clinical treatment, ultimately enhancing outcomes for individuals suffering from depression.