Do Nonspecific Factors Influence Psychotherapy Outcome?

To The Editor: We read with interest the article entitled “Treatment of Acute Posttraumatic Stress Disorder With Brief Cognitive Behavioral Therapy: A Randomized Controlled Trial,” by Marit Sijbrandij et al., in the Jan. 2007 issue of the Journal (1) . The study subjects were randomly assigned to two groups, one of which received brief cognitive behavior therapy (CBT) consisting of four weekly sessions of approximately 120 minutes each, while the comparison group remained on a waiting list and received no intervention. Assessments were made for both groups at baseline and follow-up at 1 week and 4 months. Nonspecific factors such as therapeutic alliance have long been known to influence the outcome in psychotherapies (2, 3) . In our opinion, placing the comparison group on a waiting list did not adequately control for these nonspecific factors and thus did not clearly delineate whether the short-term benefits that were noted in the intervention group were specific to the cognitive strategies that were used.

Although the two groups were comparable at baseline with regard to posttraumatic stress disorder (PTSD) and other comorbid axis I disorders, no screening was conducted for axis II disorders. It is noteworthy that the interface between PTSD and borderline personality disorder has been evaluated in depth, and implications for treatment have been identified (4) . We understand that screening for axis II disorders can be highly cumbersome; however, it might be important in studies, such as the one conducted by Sijbrandij et al., in which CBT strategies are used, which may often be ineffective in subjects with cluster B personality traits, especially subjects with borderline personality disorder for whom dialectical behavior therapy may be more effective.