Disentangling pharmacological and expectation effects in antidepressant discontinuation among patients with fully remitted major depressive disorder: study protocol of a randomized, open-hidden discontinuation trial

Background: Antidepressants are established as an evidence-based, guideline-recommended treatment for Major Depressive Disorder. Prescriptions have markedly increased in past decades, with a specific surge in maintenance prescribing. Patients often remain on antidepressants longer than clinically necessary. When attempting to stop, many patients experience adverse discontinuation symptoms. Discontinuation symptoms can be debilitating and hinder successful discontinuation. While discontinuation symptoms can result from pharmacological effects, evidence on nocebo-induced side effects of antidepressant use suggests that patients' expectations may also influence occurrence.

Methods: To disentangle pharmacological and expectation effects in antidepressant discontinuation, patients with fully remitted Major Depressive Disorder who fulfill German guideline recommendations to discontinue will either remain on or discontinue their antidepressant. Participants' expectations will be manipulated by varying verbal instructions using an open-hidden paradigm. Within the open trial arms, participants will receive full information about treatment, i.e., high expectation. Within the hidden trial arms, participants will be informed about a 50% chance of discontinuing versus remaining on their antidepressant, i.e., moderate expectation. A total of N = 196 participants will be randomly assigned to either of the four experimental groups: open discontinuation (OD; n = 49), hidden discontinuation (HD; n = 49), open continuation (OC; n = 49), or hidden continuation (HC; n = 49). Discontinuation symptom load during the 13-week experimental phase will be our primary outcome measure. Secondary outcome measures include discontinuation symptom load during the subsequent 39-week clinical observation phase, recurrence during the 13-week experimental period, recurrence over the course of the complete 52-week trial evaluated in a time-to-event analysis, and stress, anxiety, and participants' attentional and emotional processing at 13 weeks post-baseline. Blood and saliva samples will be taken as objective markers of antidepressant blood serum level and stress. Optional rsfMRI measurements will be scheduled.

Discussion: Until today, no study has explored the interplay of pharmacological effects and patients' expectations during antidepressant discontinuation. Disentangling their effects has important implications for understanding mechanisms underlying adverse discontinuation symptoms. Results can inform strategies to manage discontinuation symptoms and optimize expectations in order to help patients and physicians discontinue antidepressants more safely and effectively.

Trial registration: ClinicalTrials.gov (NCT05191277), January 13, 2022.