Sleep, circadian rhythms and physical activity in depression and anxiety: The role of ambulatory assessment tools

Depression and anxiety are highly prevalent psychiatric disorders. More than 300 million people are affected by depression and nearly the same number of people suffer from a range of anxiety disorders. Depression is ranked by the World Health Organization (WHO) as the single largest contributor to global disability, and anxiety disorders are ranked 6th. To successfully diagnose, treat and monitor depressive and anxiety disorders, wearables/mobile technologies have become promising ambulatory assessment tools in psychiatry. Ambulatory assessment tools including wrist-worn actigraphy devices and smartphones have become widely used in psychiatric research to measure core features and symptoms of psychiatric disorders: disturbances in sleep and circadian rhythm and, physical activity alterations. However, more research is needed to understand the added value of these tools in psychiatric clinical practice. This thesis focuses on examining sleep, circadian rhythm and physical activity assessed with wrist-worn actigraphy devices in depressive and anxiety disorders. To do so, data from the Netherlands Study of Depression and Anxiety (NESDA) was used. NESDA was designed to investigate the course of depressive and anxiety disorders over a period of several years and the factors that influence the development and prognosis of such disorders. 2981 participants were initially included at the baseline assessment in 2004-2007, and seen for the fifth time at the nine-year follow-up assessment wave (2014-2017) for a regular follow-up interview, including a psychiatric diagnostic interview. A sub sample from NESDA, consisting of 384 people, was selected to participate in the Ecological Momentary Assessment & Actigraphy sub-study (NESDA-EMAA). Among demographic, psychiatric and lifestyle characteristics, data from ambulatory assessment tools measuring negative and positive affect as well as actigraphy simultaneously for 2 weeks were collected at the nine-year follow-up assessment. This thesis extensively examined and demonstrated that disturbances in sleep and circadian rhythms and altered physical activity assessed with ambulatory assessment tools are associated with psychopathology. Although actigraphy-assessed sleep disturbances are not associated with depression and anxiety diagnoses, longer sleep duration assessed with actigraphy is more frequent among people with higher depressive symptoms and somatic/vegetative symptoms. In addition, higher subjective sleep quality assessed with Ecological Momentary Assessment is longitudinally associated with better affect. Low physical activity levels and dampened circadian amplitude are consistently associated with psychopathology and therefore are general indicators of depression and anxiety. However, individual differences exist and may be taken into account when providing cognitive and behavioral interventions. While more research is needed on validity, form and content of ambulatory assessments for psychiatric populations, mobile technologies are a promising to aid personalization of treatment and monitoring of treatment response. Such applications should be explored in future epidemiological and clinical studies.