Fear conditioning and extinction do not differ between trauma-exposed individuals with and without clinical diagnoses of PTSD: A pre-registered analysis of a large sample.

Post-traumatic stress disorder (PTSD) is characterized by strong and persistent emotional responses to stimuli that have previously been associated with danger. It has been argued that fear conditioning paradigms can be used as a laboratory model of this disorder, with people with PTSD showing differences in fear and extinction learning. Previous studies have been inconsistent in showing differences at either stage. This may result from a combination of small sample sizes and variations in analytic strategies. In a large sample of individuals exposed to a traumatic stressor within the past two years, we examined whether those who met DSM-5 criteria for PTSD exhibited different patterns of fear conditioning and extinction learning compared to those who did not meet PTSD criteria. Fear responses were measured using skin conductance responses (SCRs) and retrospective shock expectancy ratings. The statistical analyses were pre-registered. Participants first completed a fear acquisition phase immediately followed by the extinction phase. No group differences were seen in responses to the fear-related stimulus compared to the safety stimulus in either outcome measure for either the acquisition or extinction phase. There were no correlations between PTSD severity and the differentiated fear response. In summary, our results did not provide support for individuals with a PTSD diagnosis compared to trauma-exposed controls displaying differences in fear and extinction learning in either SCRs or subjective shock expectancy ratings. A major limitation of the study was the fixed orders of stimulus presentations, which risks confounding learning effects from order effects in the SCR data.