Extinction learning before trauma and subsequent posttraumatic stress

Objective: Fear conditioning theories propose that persistent stress reactions may occur as a result of impaired extinction learning, and a poor capacity for extinction learning may predispose some individuals to posttraumatic stress disorder development. This study indexed the extent to which deficits in extinction learning before trauma exposure are a risk factor for persistent posttraumatic stress after trauma exposure. Methods: Eighty-four firefighters were assessed during cadet training (before trauma) and 70 were reassessed within 24 months of commencing active firefighting duties (after trauma). Measures of posttraumatic stress were used before and after trauma exposure. In addition, skin conductance and corrugator electromyogram (EMG) responses were obtained during fear conditioning and extinction paradigms before trauma exposure. Results: Reduced extinction of an aversively conditioned corrugator EMG response pretrauma predicted 31% of the variance in posttraumatic stress severity. Conclusions: This result provides preliminary support for reduced extinction of a conditioned emotional response as a vulnerability factor for posttraumatic stress.