title: The psychology of HPA axis activation: Examining subjective emotional distress and control in a phobic fear exposure model.
abstract: The HPA axis plays a key role in mediating the effects of "stress" on health, but clarifying mechanisms requires an understanding of psycho-biological linkages. There has long been an implicit assumption that subjective emotional distress (e.g., fear) should activate the HPA axis. Although this assumption was challenged 25 years ago (Curtis, 1976), laboratory studies in humans are limited. In this study we sought to replicate Curtis' findings and extend it by investigating if presence or absence of stressor control shapes HPA axis reactivity in a phobic fear exposure model. We recruited 19-45-year-old specific phobia participants (n=32 spider/snake phobia; n=14 claustrophobia) and gradually exposed them to their feared object or situation while measuring hormonal (ACTH and cortisol) and subjective (emotional distress, perceived control) responses. Utilizing a dyadic yoked design, we compared HPA reactivity when the pace of exposure was controlled by participants to identical exposure given to matched participants in the absence of control. Results showed that phobic fear exposure generated intense emotional distress without a corresponding increase in HPA axis activity. Although our actual manipulation of control failed to impact HPA responses, perceived control during exposure was associated with lower cortisol, an effect that was moderated by actual availability of stressor control. Our findings replicate Curtis' findings and challenge the still common but unsupported assumption that HPA axis activity reflects subjective distress. These results also highlight the importance of both perceived and actual aspects of stressor control in understanding what is truly "stressful" to the HPA axis system.
authors.affiliation: Department of Psychology, University of Michigan, 530 Church Street, Arbor, MI 48109, USA.
authors.forename: Stefanie E
authors.initials: SE
authors.lastname: Mayer
authors.affiliation: Department of Psychiatry, University of Michigan, 4250 Plymouth Rd, Arbor, MI 48109, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Snodgrass
authors.affiliation: Department of Psychiatry, University of Michigan, 4250 Plymouth Rd, Arbor, MI 48109, USA.
authors.forename: Israel
authors.initials: I
authors.lastname: Liberzon
authors.affiliation: Department of Psychiatry, University of Michigan, 4250 Plymouth Rd, Arbor, MI 48109, USA.
authors.forename: Hedieh
authors.initials: H
authors.lastname: Briggs
authors.affiliation: Department of Psychiatry, University of Michigan, 4250 Plymouth Rd, Arbor, MI 48109, USA.
authors.forename: George C
authors.initials: GC
authors.lastname: Curtis
authors.affiliation: Department of Psychiatry, University of Michigan, 4250 Plymouth Rd, Arbor, MI 48109, USA. Electronic address: jabelson@umich.edu.
authors.forename: James L
authors.initials: JL
authors.lastname: Abelson
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000032:analysis / Q000097:blood / Q000502:physiology; D000328:Adult; D004644:Emotions / Q000502:physiology; D005239:Fear / Q000502:physiology / Q000523:psychology*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis / Q000097:blood / Q000502:physiology; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D008297:Male; D010698:Phobic Disorders / Q000523:psychology; D010913:Pituitary-Adrenal System / Q000502:physiology; D013315:Stress, Psychological / Q000378:metabolism* / Q000523:psychology*; D055815:Young Adult
chemical_list: D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone
keywords: ACTH; Control; Cortisol; Exposure; Fear; Phobia; Stress context