Uncovering complexity details in actigraphy patterns to differentiate the depressed from the non-depressed

While the negative association between physical activity and depression has been well established, it is unclear what precise characteristics of physical activity patterns explain this association. Complexity measures may identify previously unexplored aspects of objectively measured activity patterns, such as the extent to which individuals show repetitive periods of physical activity and the diversity in durations of such repetitive activity patterns. We compared the complexity levels of actigraphy data gathered over 4 weeks (similar to 40000 data points each) for every individual, from non-depressed (n=25) and depressed (n=21) groups using recurrence plots. Significantly lower levels of complexity were detected in the actigraphy data from the depressed group as compared to non-depressed controls, both in terms of lower mean durations of periods of recurrent physical activity and less diversity in the duration of these periods. Further, diagnosis of depression was not significantly associated with mean activity levels or measures of circadian rhythm stability, and predicted depression status better than these.

Automated summary

In this study, lower complexity levels were observed in the physical activity patterns of depressed individuals compared to non-depressed controls, indicating shorter durations of recurrent physical activity periods and less diversity in the duration of these periods. Additionally, diagnosing depression was found to be better predicted by these activity patterns than mean activity levels or measures of circadian rhythm stability.