The Role of Therapists' Attachment and Introject in Their Treatment Process and Outcome: A Systematic Review

Previous reviews have examined empirical evidence of the relationship between therapists' internalized relational models, including therapists' attachment styles and Sullivan's notion of introject, and the therapeutic relationship. This review expands upon previous reviews by examining the effect of therapists' internalized relational models on the treatment process (e.g., therapeutic alliance and countertransference) and treatment outcomes (e.g., symptoms and functioning) more broadly. Our systematic search identified 42 empirical studies measuring therapist's internalized relational models, defined as therapist attachment style (i.e., the way the therapist relates to others) and/or introject (i.e., the way the therapist relates to themselves), in relation to therapy process and outcome, including 35 studies on attachment, nine studies on introject and two that examined both constructs. A rigorous quality assessment was conducted; two studies were rated as ‘moderate’, and 40 were rated as ‘weak’ in quality. Based on the study findings, it appears that more securely attached therapists may have stronger working alliances and more positive therapeutic processes with their patients. Contrary to expectations, therapist attachment security does not appear to impact treatment outcomes. Therapists who relate to themselves in a more affirming way may have stronger working alliances and better treatment outcomes, but very few studies have addressed this question thus far. More rigorous research, especially on the effect of therapists' introject, is needed. Therapists may consider the potential impact of their internalized relational models on the working alliance and other treatment processes that influence therapeutic outcomes.