Schema therapy versus treatment as usual for outpatients with difficult-to-treat depression: study protocol for a parallel group randomized clinical trial (DEPRE-ST).

BACKGROUND: About one third of patients with depression are in a condition that can be termed as "difficult-to-treat". Some evidence suggests that difficult-to-treat depression is associated with a higher frequency of childhood trauma and comorbid personality disorders or accentuated features. However, the condition is understudied, and the effects of psychotherapy for difficult-to-treat depression are currently uncertain. The aim of this trial is to investigate the beneficial and harmful effects of 30 sessions of individual schema therapy versus treatment as usual for difficult-to-treat depression in the Danish secondary, public mental health sector.

METHODS: In this randomized, multi-centre, parallel-group, superiority clinical trial, 129 outpatients with difficult-to-treat depression will be randomized (1:1) to 30 sessions of individual schema therapy or treatment as usual; in this context mainly group-based, short-term cognitive behaviour or psychodynamic therapy. The primary outcome is the change from baseline in depressive symptoms 12 months after randomization, measured on the observer-rated 6-item Hamilton Rating Scale for Depression. The secondary outcomes are health-related quality of life assessed with the European Quality of Life 5 Dimensions 5 Level Version, functional impairment assessed with the Work and Social Adjustment Scale, psychological wellbeing assessed with the WHO-5 Well-being Index, and negative effects of treatment assessed with the Negative Effects Questionnaire. Exploratory outcomes are improvement on patient self-defined outcomes, personal recovery, anxiety symptoms, anger reactions, metacognitive beliefs about anger, and perseverative negative thinking. Outcomes will be assessed at 6, 12, and 24 months after randomization; the 12-month time-point being the primary time-point of interest. Outcome assessors performing the depression-rating, data managers, statisticians, the data safety and monitoring committee, and conclusion makers for the outcome article will be blinded to treatment allocation and results. To assess cost-effectiveness of the intervention, a health economic analysis will be performed.

DISCUSSION: This trial will provide evidence on the beneficial and harmful effects, as well as the cost-effectiveness of schema therapy versus treatment as usual for outpatients with difficult-to-treat depression. The results can potentially improve treatment for a large and understudied patient group.

TRIAL REGISTRATION: ClinicalTrials.gov NCT05833087. Registered on 15th April 2023 (approved without prompts for revision on 27th April 2023).