Date of Award

Fall 2009

Degree Type


Degree Name

Doctor of Philosophy (PhD)

Graduate Group


First Advisor

Jacques P. Barber


From the psychotherapy outcome literature, many have inferred that either theory-specific techniques or interventions common to all therapies are what produce symptom change. However, such conclusions are premature because (a) too few direct tests have been conducted of how variation in the levels of either specific or common factor interventions relate to outcome, (b) those prior investigations of specific and common factors and outcome have often been limited to examining linear relations between intervention use and outcome when curvilinear functions might better model their association, and (c) most studies of psychotherapy and outcome have failed to consider how interventions specific to theoretical orientations other than that being studied (i.e., interventions not intended to be in the specific treatment under investigation nor common to all therapies) might also contribute to outcome. In this thesis, I present two studies investigating the relation of interventions from a number of different therapy systems to subsequent symptom improvement in behavioral therapy for Obsessive-Compulsive Disorder (OCD) and psychodynamic therapy for Major Depressive Disorder (MDD). Theory-specific techniques were prominent in both therapies (e.g., behavioral techniques in behavioral therapy, psychodynamic techniques in dynamic therapy), and moderate levels of specific factors were related to better outcome than were higher or lower levels in each treatment. Common factor techniques were among the highest reported interventions in both treatments, but were not predictive of symptom improvement in either therapy. Interventions from other theoretical orientations were present in both therapies, but in such a way that individual techniques appeared to be selected for use based on their congruence with the theoretical orientation of the treatment. In behavioral therapy, no other types of interventions contributed to outcome more than behavioral interventions. In psychodynamic therapy, moderate levels of process-experiential techniques were associated with better outcome than were higher or lower levels. Further research needs to document how specific, common, and unintended factors occur in different psychotherapies and how such interventions might relate to outcome in complex ways before conclusions can be made about the mechanisms of therapy.