The Effectiveness of Psychological Interventions for Common mental disorders (EPIC): Protocol of a pragmatic randomized waitlist-controlled superiority trial

Background : Primary sector settings are facing a pressing need for accessible and evidence-based psychological treatments. Despite this fact, only relatively few studies have used a rigorous randomized controlled trial (RCT) design to investigate the effect of psychotherapy in a naturalistic setting, where therapists possess a high degree of freedom to organize treatment and select their own methods. The main objective of the current study is to test the efficacy of psychotherapy for common mental disorders delivered in routine practice in Denmark, in comparison to a waitlist control group. Supplementary objectives are to assess potential predictors of symptom development while in treatment and while placed on a waitlist for treatment. Methods : A total of 308 clients will be recruited from 20 psychologists practicing in the primary sector and randomized to a) psychotherapy starting within two weeks or b) a waitlist for treatment. The primary outcome will be the rate of change in symptoms of depression and anxiety, measured using the Patient Health Questionnaire Anxiety and Depression Scale (PHQ-ADS). This outcome will be measured before treatment, bi-weekly, and after approximately four, eight, and 16 months of treatment. Secondary outcomes will include functional impairment (Sheehan’s Disability Scale), quality of life (World Health Organization Index), and perceived stress (Cohen’s Perceived Stress scale), measured before treatment and after four, eight, and 16 months of treatment, as well as satisfaction with treatment (Client Satisfaction Questionnaire), and negative treatment outcomes (Negative Events Questionnaire), measured after four months of treatment. Potential client predictors of symptom change in treatment and while on the waitlist will include personality pathology (Levels of Personality Functioning Scale), emotion regulation (Emotion Regulation Skills Questionnaire), and coping strategies (Brief-COPE inventory). Process predictors include the working alliance (Working Alliance Inventory) and the therapist’s therapeutic approach (Multitheoretical List of Therapeutic Interventions). Discussion : This RCT will be the first of its kind to provide evidence on the efficacy of the psychotherapy conducted in routine practice in Denmark. Moreover, the predictor studies may help identify subpopulations of clients who are differentially impacted by the treatment or by time spent on a waitlist, thereby contributing to precision mental health care. Trial registration : ClinicalTrials.gov, ID: NCT06916429. Registered on March 31st, 2025: https://clinicaltrials.gov/study/NCT06916429