Fear Extinction

Barbara Olasov Rothbaum et al. (2012) · Biological psychiatry

This randomized pilot study with 137 civilian trauma patients explored whether starting psychotherapy within hours of a traumatic event, before the memory of the event fully consolidates (the process by which an experience becomes a stable, long-term memory), could prevent posttraumatic stress disorder (PTSD) from developing. The intervention was a modified version of prolonged exposure (PE), a therapy that reduces conditioned fear responses by having a person repeatedly revisit a feared memory in a safe setting until the fear response diminishes, a process known as fear extinction. Because most PTSD treatments begin only after symptoms are already established, this trial tested the therapy as prevention rather than as treatment of chronic illness. Participants were adults aged 18 to 65 who arrived at a Level One trauma center emergency department within 72 hours of a qualifying trauma; 137 were randomly assigned to three one-hour sessions of modified PE, delivered one week apart and beginning in the emergency department, or to assessment only. The modified PE sessions involved guided recounting of the trauma memory, discussion of the traumatic experience, and take-home exposure exercises. Blinded evaluators measured posttraumatic stress severity with a structured clinical interview (the PSS-I) and depression with a standard self-report questionnaire (the BDI-II) at 4 and 12 weeks after enrollment. Participants who received the intervention reported significantly lower posttraumatic stress severity than the assessment-only group at 4 weeks (19.09 vs. 24.54 points, p = 0.02 for the overall treatment effect) and 12 weeks (15.47 vs. 20.33 points), representing a medium-sized benefit (Cohen's d of 0.34 to 0.38, a standard measure of effect strength where 0.2 is considered small and 0.8 is considered large). By 12 weeks, significantly more intervention participants no longer met PTSD criteria than controls (74% vs. 53%, p = 0.04). Depression scores at 4 weeks were also significantly lower in the intervention group (p < 0.01, d = 0.35). The benefit was largest among rape victims, who showed a large effect (d = 0.70) at 4 weeks, notable because sexual assault carries among the highest known risk of developing PTSD. The intervention did not significantly reduce symptoms tied to participants' earlier, unrelated traumas, suggesting its effect was specific to the event that brought them to the emergency department. The findings suggest that exposure-based psychotherapy can be safely delivered within hours of trauma, in an emergency department, before a traumatic memory becomes consolidated. The authors note important limitations: no baseline PTSD measure was collected, since assessing symptoms so soon after trauma was judged invalid, so only between-group comparisons were possible; the sample was pilot-sized and not powered for smaller effects; and roughly a quarter to a third of participants did not complete follow-up assessments. The authors describe the results as establishing feasibility and call for larger replication trials.