The prologue to depression: a tale about complex dynamics and simple trends

This thesis regards the processes of change that people undergo when they develop depressive symptoms. In the TRANS-ID (transitions in depression) Tapering study, over 50 patients were monitored with 5 questionnaires each day for a period of 4 months during and shortly after antidepressant tapering. We found that in some patients depressive symptoms returned gradually over a period of weeks or months, sometimes so gradually that the patient themselves did not notice the change. In other patients, depressive symptoms returned very suddenly, sometimes even within a day. In both cases it would be useful if signals of returning depression could be detected in an early stage, as this could help prevent depressive recurrence in the future. We investigated two ways of doing this: (1) by investigating general indicators of instability that have been shown to precede transitions in a wide range of natural systems, and (2) by monitoring feelings of restlessness, a symptom that many patients experience in the stages preceding depression. Even though general indicators of instability could be found in some participants who experienced depressive recurrence, these signals were not found consistently enough to accurately predict depression. However, by monitoring restlessness we could predict whether depressive symptoms would recur in the near future in over 70% of participants. This predictive accuracy was comparable or slightly better than the predictive accuracy of state-of-the-art methods using more classically obtained data. Monitoring restlessness appears to be a promising new method to detect depressive symptoms in an early stage.