Date of Award


Document Type


Degree Name

Philosophy (Ph.D)



First Advisor

William F Chaplin

Second Advisor

Raymond A DiGiuseppe

Third Advisor

Tara Rooney


This research aims to establish that considerable differences exist between therapists on how much their clients improve in treatment and understand the factors that contribute to such variability. Therapists’ sex, personality, and similarity of their personality with their clients’ personality were examined as moderators of change in treatment outcome. Findings must be interpreted with caution due to limitations of the dataset which make therapists effects hard to separate from client effects. There is variation around the amount of change therapists produce in their clients; however, this variation is much smaller compared to the variance among clients. Female therapists consistently had clients with better improvement, however, this result was statistically significant for only one symptom subscale. Therapists with higher Openness had clients with improved working alliance over time, but worsening symptom levels. Therapists’ Neuroticism moderated change in working alliance but symptom levels. Therapists’ interpersonal Warmth and Extraversion moderated change in symptom levels. There were no differences in treatment outcome amongst similar/dissimilar overall personality profiles of therapist-client dyads. Case transfer did not have an overall negative impact on treatment outcome; however, this result must be interpreted within context that time is a confounding variable.