The impact of Cluster C personality disorders on the outcome of contrasting psychological treatments for depression

Twenty-seven of 114 depressed clients, stratified for severity of depression, obtained a Diagnostic and Statistical Manual of Mental Disorders (3rd ed.; DSM-III; American Psychiatric Association, 1980) diagnosis of Cluster C personality disorder, that is, avoidant, obsessive-compulsive or dependent personality disorder (PD clients), whereas the remaining 87 did not (non-personality-disorder [NPD] clients). All clients completed either 8 or 16 sessions of cognitive-behavioral (CB) or psychodynamic-interpersonal (PI) psychotherapy. On most measures, PD clients began with more severe symptomatology than NPD clients. Among those who received PI therapy, PD clients maintained this difference posttreatment and at 1-year follow-up. Among those who received CB therapy, posttreatment differences between PD and NPD groups were not significant. Treatment length did not influence outcome for PD clients. PD clients whose depression was also relatively severe showed significantly less improvement after treatment than either PD clients with less severe depression or NPD clients.