Estimating the Smallest Worthwhile Difference (SWD) of Psychotherapy for Depression: Protocol for a Cross-Sectional Survey

BackgroundPsychotherapy is proven efficacious for the treatment of depression. However, the patient-perceived importance of its effect is not fully appreciated in the evidence base. The smallest worthwhile difference (SWD) represents the smallest beneficial effect of an intervention that patients deem worthwhile given the harms, expenses, and inconveniences associated with the intervention, and facilitates the interpretation of patient perceived importance of an intervention. MethodsThe proposed study will estimate the SWD of the American Psychological Association recommended psychotherapies for depression treatment with English-speaking American and British respondents aged 18 and older. Respondents will be recruited using research participant crowdsourcing sites. The SWD will be estimated using the Benefit-Harm Trade-off Method, presenting survey respondents with variable, hypothetical magnitudes of psychotherapy outcomes to find the smallest acceptable effect over a no treatment alternative. The overall average SWD, and subgroup distributions by participant depression treatment experiences and depression symptomology will be described. Participant characteristics will be included in a regression model to explore associated variability in the SWD. Expected ResultsWe expect to find an estimate of the SWD for psychotherapy in the treatment of depression. Further, we expect that the SWD will vary between clinical subgroups based on depression symptomology and treatment experiences. We expect there to be variation between those who demonstrate depression symptoms consistent with a depressive disorder, based on PHQ-9 scores or self-reported diagnosis history. We think that the findings from this project will inform the treatment decision process about psychotherapy during the clinical consultation for people with depression.