Rationale: A current issue in the frame of antidepressant medication is the rise of long-term antidepressant use associated with noticeable adverse effects such as withdrawal effects, sexual difficulties, weight gain and emotional numbness. A key factor hindering patients in the discontinuation of antidepressant medication is the emergence of discontinuation symptoms, reported by over half of fully remitted patients discontinuing antidepressants. To date, there is no study examining open-label placebo responses on antidepressant discontinuation symptoms. However, several findings imply that open-label placebos may support the discontinuation process in remitted depressed patients. The susceptibility to placebo responses is encouraged by findings indicating substantial placebo effects in antidepressant trials (67-82%). Additionally, evidence suggests the central role of expectation effects influencing the course of antidepressant discontinuation. Open-label placebos have been found to work through the generation of positive expectations, induced by a positive framing (e.g. verbal instructions). A recent meta-analysis suggests a medium to large effect size of open-label placebos. Regarding the treatment of antidepressant discontinuation symptoms, open-label placebos have the potential to reduce symptoms not only by inducing positive expectations, but also by triggering automatic (positive) responses to the intake of a pill (i.e. conditioning).The aim of this study is to investigate the effect of open-label placebos on antidepressant discontinuation symptoms in fully remitted depressed patients.

Methods: In the proposed study, a pilot sample will discontinue their antidepressant intake under extensive medical and psychological supervision, according to the national and international guidelines over a 13-week course. After a run-in week and the baseline assessment, antidepressant medication will be gradually reduced with individualized discontinuation plans over a period of 4 weeks. Weekly measurements serve to monitor the condition of the participants. After discontinuation, patients will be monitored (with biweekly study visits) for another 8 weeks (experimental phase). Finally, a follow-up measurement 6 months after the study start constitutes long-term monitoring and the assessment of relapse after antidepressant discontinuation. During the experimental phase, patients experiencing moderate discontinuation symptoms are allocated to the intervention group, aimed to examine the effect of open-label placebo on antidepressant discontinuation symptoms. For this purpose, N-of-1 trials comprising multiple crossovers (A: open-label placebo; B: no treatment) within each individual, and varying in a biweekly rhythm, are applied. Patients are randomized to different treatment orders (ABAB; BABA). Twice daily smartphone-measurements are implemented to assess discontinuation symptoms, expectations and mood. Additionally, study visits consist of extensive measurements related to discontinuation symptoms, depressive symptomatology, psychological well-being and treatment expectations. These serve as observational measurement of different effects related to antidepressant discontinuation. During the experimental phase, outcome assessors will be blind to the randomization (i.e. treatment order) of the patients.

Objectives: At the end of the study, the investigators will determine whether open-label placebo reduces negative side effects caused by antidepressant discontinuation by aggregating the N-of-1 trials. Underlying mechanisms such as treatment expectations, as well as the relation to depressed mood, will be under explorative investigation. Additionally, the course of discontinuation symptoms, depressive symptoms (self-report and expert-rated) and treatment adherence during the entire study will be explored. Therefore, potential modulators such as psychopathology, demographics, adverse events, expectations, prior experience, subjective stress, side effects of antidepressants and anxiety vs. depression (trait/state) will be taken into account in data analyses.