Objectives. To present an interview-based 7-item Suitability for Psychotherapy Scale (SPS) created to evaluate suitability for short- and long-term therapy, and to assess its reliability, validity, and prediction.
Design. Reliability of the SPS was evaluated by measuring both repeatability and agreement (cross-sectional design). Validity of the SPS was evaluated by measuring both criterion and discriminating validity (cross-sectional design). Prediction of the SPS was evaluated using a cohort study design.
Methods. Suitability of 326 psychiatric outpatients from the Helsinki Psychotherapy Study was assessed at baseline with the SPS, and a summary score of the seven items was formed. Reliability of the SPS was evaluated using kappa coefficients and validity using linear models. The ability of the SPS to predict changes in symptoms (SCL-90-GSI) during a 1-year follow-up was measured. The analysis of validity and prediction of SPS were based on data of all 326 patients and analysis of reliability of SPS on a sample of 28 patients.
Results. Both the repeatability of the interviewers’ assessments over 3 years and agreement between interviewers and reference were fair or good. An association of the SPS with personality functions but not with psychiatric symptoms supported criterion and discriminating validity of the SPS. The SPS also significantly predicted changes in symptoms during follow-up.
Conclusions. The SPS appeared to be a valid and reliable method for assessing pre-treatment suitability, with good prediction of psychotherapy outcome.