Estimating effectiveness of school-based counselling: Using data from controlled trials to predict improvement over non-intervention change.

Background: There is a growing body of data to show that participation in school‐based counselling is associated with significant reductions in psychological distress. However, this cannot be taken as evidence that school‐based counselling is effective, as improvements may have happened without the intervention. Aims: The purpose of this study was to develop a method of estimating the amount of ‘natural’ change that might be expected in young people who would attend school‐based counselling, such that the effects of the intervention over and above this amount could be identified. Method: Young Person's CORE (YP‐CORE) scores from 74 participants allocated to waiting list control conditions in four pilot trials of school‐based counselling in the UK were re‐analysed using regression models, and a formula was found for estimating the outcomes for young people were they not to receive counselling. This was termed their Estimated Non‐intervention Outcome (ENO), and could then be compared against the young person's Actual Outcome (AO), to give an estimated intervention effect (EIE). Results: The formula for the ENO was 4.17 + 0.64 × baseline score. Using this, we calculated a mean EIE for 256 young people in a cohort evaluation study of school‐based counselling, which showed that the counselling was associated with large and significantly greater change than would be expected without the intervention (Cohen's d = 0.91). Discussion: The method presented in this paper is a simple means for improving the accuracy of estimations of treatment effectiveness, helping to adjust for changes due to spontaneous recovery and other non‐treatment effects. [ABSTRACT FROM AUTHOR]