Upon awakening, there is normally a surge in cortisol, a steroid hormone produced by the adrenal gland and released in response to stress. Now, UK researchers report that this response is absent in adolescent boys with Asperger syndrome, which may explain some of the symptoms of the condition, such as the need for routine and resistance to change.

Among other functions, the ability to adapt to change is controlled by the hypothalamic-pituitary-adrenal axis, which controls the dramatic increase in cortisol upon awakening, referred to as "the cortisol awakening response," the study team explains in an article in press in the journal Psychoneuroendocrinology.

"The cortisol awakening response is a robust and reproducible neuroendocrine phenomenon which has been positively correlated with psychological and physical well-being,"

they add.

Dr. Mark Brosnan from University of Bath and colleagues say their research points to a lack of response in the hypothalamic-pituitary-adrenal axis in individuals with Asperger syndrome, which may help explain why these individuals have difficulties if there are minor changes in their routine or environment.

In the study, the investigators measured the cortisol in saliva of 20 adolescent males with Asperger syndrome and 18 age-matched controls at the time of awakening and 30 minutes later.

While a significant cortisol awakening response was clearly evident in the control group, this was not the case in the Asperger group.

"In our study, the typical marked rise in cortisol, peaking around 30 minutes after waking, was found to be of significant magnitude only in the typically developing control group. Therefore, Asperger syndrome, at least in adolescent males, appears to be characterized by an impaired cortisol awakening response,"

Brosnan and colleagues write.

Brosnan and colleagues say further research is needed to address this "intriguing phenomenon" in Asperger syndrome.