A new study confirms what many long suspected about the use of service dogs with children who have autism: they help reduce stress and behavior problems.

Canadian researchers tracked 42 children with autism who were paired with specially-trained service dogs. Researchers then measured the cortisol present in the children’s saliva — which correlates to a person’s stress level — before the dogs were placed with the kids, while the dogs were in use and after the dogs were removed.

Typically, cortisol spikes a half hour after a person wakes up and then decreases throughout the remainder of the day. Before receiving the dogs, the children showed a 58 percent rise in cortisol after waking. That amount dropped to 10 percent after the dogs were placed with the families. When the dogs were later removed, the children with autism experienced a rise in cortisol levels to 48 percent.

“Our findings showed that the dogs had a clear impact on the children’s stress hormone levels,” said Sonia Lupien, a professor at the Université de Montréal who worked on the study which was published in the journal Psychoneuroendocrinology. “I have not seen such a dramatic effect before.”

In addition to measuring cortisol levels, Lupien and her colleagues had parents complete questionnaires about the children’s behavior both with and without the dogs. On average, parents reported 25 behavior issues while living with the dog versus 33 otherwise.

The study is believed to be the first to measure the physiological impact of service dogs on children with autism.

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