Cortisol helps the brain respond to change
Children with Asperger's Syndrome may dislike change to their routine because of their different levels of the stress hormone cortisol, a study suggests.
The hormone is believed to make the brain more alert, and more able to cope with changes in the environment.
Writing in Psychoneuroendocrinology, researchers noted children with the autistic condition do not experience the normal morning "surge" of cortisol.
This may explain their need for routine and aversion to change, they suggested.
"Cortisol is one of a family of stress hormones that acts like a 'red alert' that is triggered by stressful situations allowing a person to react quickly to changes around them," said Mark Brosnan, a psychologist at Bath University.
"In most people, there is a two-fold increase in levels of this hormone within 30 minutes of waking up, with levels gradually declining during the day as part of the internal body clock.
"Our study found that the children with AS [Asperger's Syndrome] didn't have this peak, although levels of the hormone still decreased during the day as normal.
"Although these are early days, we think this difference in stress hormone levels could be really significant in explaining why children with AS are less able to react and cope with unexpected change."
People with Asperger's are usually more mildly affected than those with autism but they can nevertheless experience significant problems coping with daily life.
Often of average or above intelligence, they may perform well at school but have difficulties with communication and forming social relationships.
The team from the universities of Bath and Bristol hope their findings will improve understanding of the symptoms as a response to what the child sees as a stressful situation, rather than a behavioural problem.
Strategies can then be developed by parents, carers and teachers for avoiding situations which might cause distress.
"We have long known that anxiety is one of the key problems, and people use various coping strategies including cognitive therapy and small doses of anti-anxiety medicine," said Richard Mills, research director of Research Autism.
"We welcome these conclusions because anything that furthers our understanding of the nature of this anxiety is very helpful indeed," he added.
"We would now like to see similar work in adults."