Objective: For eating disorders, a vast number of investigations have demonstrated the efficacy of psychological treatments. However, evidence supporting the impact of therapeutic process aspects on outcome (i.e., process-outcome research) has not been disentangled.
Method: Using the Generic Model of Psychotherapy (GMP) to organize various process aspects, a systematic literature search was conducted on psychological treatment studies for anorexia nervosa, bulimia nervosa, binge-eating disorder, and eating disorders not otherwise specified.
Results: Improved outcomes resulted for family-based treatment compared to individual treatment, for individual compared to group treatment, booster sessions, and positive patient expectations (GMP contract aspect); for nutritional counseling and exercising but not exposure with response prevention as adjunct interventions (therapeutic operations); for highly motivated patients and, to a lesser extent, for therapeutic alliance (therapeutic bond); as well as for rapid response and longer overall treatment duration (temporal patterns). Regarding other GMP aspects, studies on self-relatedness were completely lacking and in-session impacts were rarely investigated.
Discussion: As most studies assessed only a limited number of process aspects, the ability to draw conclusions about their overall impact regarding outcome is rather limited. Therefore, future process-outcome research is needed beyond investigations of treatment efficacy for eating disorders
