Persistence of safety behaviors or the acquisition of new ones? The effect of cross-US reinstatement in safety behaviors

Exposure to a stressful trauma after successful treatment can lead to relapse, known as fear reinstatement. In the laboratory, fear reinstatement involves re-exposing individuals to an aversive unconditioned stimulus (US) after successful extinction learning, leading to the reinstatement of fear to a previously threatening conditioned stimulus (CS). While fear reinstatement is typically thought to evoke the return of old fear, preliminary evidence suggests that using a qualitatively different US during reinstatement can elicit new fear (i.e., this new US is expected to follow the CS instead of the US used in training). This study aimed to expand on this finding by examining safety behaviors, a behavioral response that minimizes US onset. To this end, participants first acquired conditioned fear and safety behaviors to the CS, followed by extinction learning to it. On the second day, some participants encountered a novel reinstatement US (Cross-US), while others received either the same US as in acquisition for reinstatement (Same-US) or no reinstatement manipulation (No-US). After reinstatement manipulation, the Cross-US group showed a larger increase in US avoidance and US expectancy to the novel US compared to the other groups. Our findings suggest that reinstatement elicits new fear and safety behaviors, underlying that treatment might benefit from addressing a range of safety behaviors.