Knowledge acquisition following internet-based cognitive behavioural therapy for loneliness-A secondary analysis of a randomised controlled trial

Background and objectives: Knowledge about a condition and how to treat it is part of most cognitive behavioural therapies. This is particularly relevant for self-help treatments such as internet-based CBT, which is commonly delivered in the form of didactic materials. The role of knowledge acquisition in treatment outcomes is an understudied area. The present study sought to investigate knowledge acquisition as part of an ICBT trial targeting loneliness and discern its role in the outcome of treatment. Methods: We used secondary data from a randomised controlled trial of ICBT targeting loneliness with 73 participants. A knowledge test including certainty ratings was constructed and used to investigate whether knowledge increased for the treatment group in comparison to the control group, whether changes in knowledge predicted changes in loneliness during the treatment phase, and how the acquired knowledge related to outcomes at a two-year follow-up. Multiple linear regression models were used to analyse the data. Results: The treatment group had significantly higher knowledge scores compared to the waitlist group at posttreatment, both in terms of correct answers (Cohen's d = 0.73) and certainty-weighted sum scores (Cohen's d = 1.20). Acquired knowledge did not predict reductions in loneliness in the short-term, and neither loneliness ratings nor use of treatment techniques in the long-term. Limitations: The sample size was relatively small, which limits the statistical inferences. Conclusions: Knowledge of treatment relevant principles increase as part of the treatment in ICBT for loneliness. This increase was not related to other short- and long-term outcomes.