Mechanisms and effects of acute stress on extinction learning: Two randomised-controlled trials of stress-enhanced CBT for spider phobia

Abstract

This thesis investigated the application of stress as a pathway to reduce different relapse phenomena and the mechanisms by which this may occur. To address these aims, a systematic review, pilot and small randomised-control study (RCT) were conducted. The systematic review indicated stress generally leads to greater treatment outcomes in the short and long-term (4-6 weeks). An Integrated Model of Stress-Augmentation was used to synthesise findings and suggest mechanisms for investigation. The other studies extended previous findings by investigating the potential for stress to reduce relapse associated with a change in context (renewal) and following an extended period of time (spontaneous recovery) within clinical samples. The role of stress hormones (cortisol and noradrenaline), expectancy of harm and attention were explored as mediators of these effects. Study 1 and 2 included participants aged 18-60, with a fear of spiders, who were randomly allocated to receive a behavioural stress (socially evaluated cold presser task) or control task 25 minutes prior to two virtual-reality exposure sessions. Findings revealed stress improved treatment outcomes at posttreatment, 3-month and 7-month follow-up periods, as measured by spider phobic questionnaires. No effect of stress on renewal of fear was found following test in a novel context. During exposure, stress enhanced initial expectancy of harm, but had no effect on participants engagement with the spider. Mediation analysis revealed cortisol partially mediated the long-term, but not the short-term, benefits of stress on treatment outcomes, confirming previous studies on the memory-enhancing effect of stress. Together, results illustrate stress has the potential to reduce spontaneous recovery of fear, partially accounted for by cortisol, but does not affect renewal of fear assessed in the shortterm.