Development and validation of a 6-item working alliance questionnaire for repeated administrations during psychotherapy.

Recently, researchers have started to measure the working alliance repeatedly across sessions of psychotherapy, relating the working alliance to symptom change session by session. Responding to questionnaires after each session can become tedious, leading to careless responses and/or increasing levels of missing data. Therefore, assessment with the briefest possible instrument is desirable. Because previous research on the Working Alliance Inventory has found the separation of the Goal and Task factors problematic, the present study examined the psychometric properties of a 2-factor, 6-item working alliance measure, adapted from the Working Alliance Inventory, in 3 patient samples (ns = 1,095, 235, and 234). Results showed that a bifactor model fit the data well across the 3 samples, and the factor structure was stable across 10 sessions of primary care counseling/psychotherapy. Although the bifactor model with 1 general and 2 specific factors outperformed the 1-factor model in terms of model fit, dimensionality analyses based on the bifactor model results indicated that in practice the instrument is best treated as unidimensional. Results support the use of composite scores of all 6 items. The instrument was validated by replicating previous findings of session-by-session prediction of symptom reduction using the Autoregressive Latent Trajectory model. The 6-item working alliance scale, called the Session Alliance Inventory, is a promising alternative for researchers in search for a brief alliance measure to administer after every session.