Study addresses role of personality in treatment response of PTSD

In the last 2011 issue of Psychotherapy and Psychosomatics a group of Dutch investigators addresses the role of personality in treatment response of post-traumatic stress disorder.

Research has identified trauma-focused cognitive-behavioral therapy (TFCBT) as an effective treatment for post-traumatic stress disorder (PTSD). However, a substantial minority of PTSD patients do not sufficiently benefit from TFCBT. Many clinicians would explain differential PTSD treatment outcome at least partly in terms of their patients' personality characteristics. This study explores the Five-Factor Model (FFM) personality traits as moderators of dropout and treatment response in PTSD patients. The FFM (neuroticism, extraversion, openness to experience, agreeableness, and conscientiousness) has established itself as a widely accepted and extensively researched personality model, and may potentially influence PTSD treatment outcome in various ways. Data were obtained from patients meeting DSM-IV criteria for PTSD in a previous randomized controlled trial. FFM traits were measured at baseline with the NEO-Five Factor Inventory . Self-rated PTS symptoms were measured at baseline and posttest with the Impact of Event Scale. PTSD diagnostic status was established at baseline and posttest with the Structured Clinical Interview for DSM-IV Axis I disorders. Treatment consisted of a maximum of 10 1.5-hour sessions of TFCBT or structured writing therapy, and was compared to waitlist control (WLC). Forty-one randomized controlled trial participants (33.3%) dropped out and did not complete the posttest. None of the interactions between FFM traits and study condition were significant (all p > 0.10), indicating that the FFM traits did not moderate dropout. For the 82 completers (66.7%), baseline PTS symptoms were strongly associated with treatment outcome in each FFM multiple regression model (all p < 0.001), as was study condition (i.e. receiving active treatment; all p < 0.001). In contrast, no main effects were observed for any of the FFM traits (all p > 0.10). Lower scores on openness to experience were more strongly associated with posttest PTS symptoms after active treatment than after WLC, indicating that this FFM trait moderated PTSD treatment outcome. No significant interactions were observed between active treatment and neuroticism, extraversion, or agreeableness (all p > 0.05), and a marginally significant interaction was observed between active treatment and conscientiousness (p = 0.05).

The main findings of this study can be summarized as follows. First, baseline self-reported PTS symptoms were predictive of posttest levels of PTS symptoms. This is in line with previous studies, which in fact identified pretreatment PTS severity as the only consistent predictor of PTSD treatment outcome to date. Second, while no main effects for FFM traits were observed, openness to experience, and possibly conscientiousness, moderated self-reported PTS symptoms, such that patients with lower scores on these personality traits reported (slightly) more PTS symptoms after completing treatment compared to patients receiving no treatment. This effect was of small magnitude, and did not manifest in differential probabilities of achieving a no-PTSD diagnostic status after active treatment or WLC. No evidence was found for FFM traits as moderators of dropout.

In terms of clinical implications, these findings confirm that baseline PTS severity matters, and in fact matters more than individual personality differences, in predicting PTSD treatment outcome. Clinicians may be advised to be sensitive to extreme standings on openness to experience and conscientiousness, but by and large these effects are considerably less predictive of treatment response than initial symptom severity and do not appear to impact diagnostic status following treatment. Personality thus appears to be of more importance as a vulnerability factor than as a treatment response factor in the context of discrete anxiety disorders for which specific evidence-based protocols are available.