Building physiological toughness: Some aversive events during extinction may attenuate return of fear.

BACKGROUND AND OBJECTIVES: Although exposure therapy is an effective treatment for anxiety disorders, fear sometimes returns following successful therapy. Recent literature in animal models indicates that incorporating some aversive events into extinction training may offset these return of fear effects.

METHODS: The effect of occasional reinforced extinction trials was investigated in a sample of thirty-nine participants using a fear conditioning and extinction paradigm. Participants either underwent traditional extinction procedures during which the conditional stimulus which had been paired with the unconditional stimulus (US) during acquisition training (CS+) was presented alone with no presentations of the US or partially reinforced extinction during which there were several unpredicted CS+/US pairings.

RESULTS: As measured by skin conductance responses, physiological fear responding remained elevated during extinction for participants who experienced partially reinforced extinction; however, these participants demonstrated protection from rapid reacquisition effects. Results from the subjective US-expectancy ratings did not provide evidence of protection against rapid reacquisition in the partially reinforced extinction group; however, there was evidence of protection from spontaneous recovery effects. Lastly, as measured by valence ratings, it was unclear whether partially reinforced extinction provided protection from fear recovery effects.

LIMITATIONS: Although participants who experienced partially reinforced extinction demonstrated protection from rapid reacquisition as measured by skin conductance responses, they also demonstrated significantly higher levels of physiological fear responding during extinction which made the results of the spontaneous recovery test more difficult to interpret.

CONCLUSIONS: Occasional CS-US pairings during extinction may protect against return of fear effects. Clinical implications are discussed.