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Hypothalamic-Pituitary-Adrenal (HPA) axis activity in adults with intellectual disabilities: A preliminary investigation
Presland, A.D., Broughton, S. , Luke, L.R., Wheeler, E., Chan, S., WATSON, P.C. , Fairchild, G., Clare, I.C.H. , and Ring, H.A.
Journal of Intellectual Disability Research, 57(6), 539-551
Year of publication:
Background The HPA axis is a marker of physiological arousal, and exhibits a characteristic pattern of diurnal activity. The daily cortisol profile has been examined extensively in both typical (healthy) and clinical populations and is atypical in a number of clinical disorders. However, there is a dearth of studies focussing on the cortisol profile in adults with intellectual disabilities. This paper reports a preliminary investigation into the nature of the cortisol profile in adults with mild or moderate intellectual disabilities, and provides an opportunity to comment on the challenges of physiometric research in this population. Methods Thirty-nine adults with mild or moderate intellectual disabilities each donated saliva samples for cortisol analysis, at multiple times between waking and evening, on two consecutive days. A comparison between these data and the published literature permitted a descriptive assessment of the Cortisol Awakening Response (CAR) and diurnal profile in this population. A variety of psychometric measures and an assessment of behavioural history were also collected in order to describe aspects of the participants’ emotional and behavioural state. Results Individuals with intellectual disabilities exhibited a topographically similar diurnal cortisol profile to that of the typical, healthy, adult population. However, the findings also tentatively suggest a blunted CAR, warranting further investigation. There was some evidence for an effect of anxiety and recent aggression on measures of cortisol secretion. Conclusion While more work is required to characterise the CAR fully, the results provided no indication that the diurnal cortisol profile among people with intellectual disabilities differs from that of the typical population. This study demonstrates that, though challenging, it is possible, and acceptable to participants, to collect repeated physiological measures from men and women with mild and moderate intellectual disabilities.