A Study of the Associations Between Clusters of Posttraumatic Stress Symptoms and Threat Reactivity

Aberrant threat reactivity has been implicated in the pathophysiology of posttraumatic stress disorder (PTSD). However, prior studies on the relation between PTSD and threat reactivity have yielded inconsistent results. One factor that may contribute to mixed results is the heterogeneity of PTSD. In particular, prior factor analytic studies have found that PTSD consists of four overlapping, but qualitatively distinct clusters of symptoms – re-experiencing, avoidance, negative cognition and mood, and hyperarousal. If these factors are indeed distinct, then they may also be characterized by distinct patterns of threat reactivity. The present study therefore examined how current and past clusters of PTSS relate to multiple indices of threat reactivity – startle potentiation to unpredictable (U-threat) and predictable aversive stimuli (P-threat), and the evoked potential error-related negativity (ERN) – in a sample of trauma-exposed individuals who were recruited as part of two larger investigations (N = 258 for startle analyses, and N = 173 for ERN analyses). There were no associations between any current or past PTSS clusters and ERN, or startle to P-threat. Current avoidance, negative cognition/mood, and hyperarousal PTSS were each associated with blunted startle potentiation to U-threat. However, multivariate models in which all current PTSS clusters were entered simultaneously as predictors revealed that there was no unique association between any clusters of PTSS and U-threat. Post-hoc analyses instead revealed a negative relation between the overall severity of current PTSS (i.e., total symptoms across all clusters) and U-threat startle. This negative association was specific to current PTSS, relative to past PTSS. This pattern of results suggests that blunted reactivity to U-threat is an epiphenomenon of more severe PTSS. Alternatively, there may be specific symptoms within each cluster of current PTSS that drove this effect. Additional implications and possible future directions are discussed.