University of Denver Autumn 2025

“ Montana has given me the

opportunity to live again. I can be a part of the world, a part of the community, and a part of life. ” Ashleigh Williams

that increase heart rate, blood pressure, and energy. The hypothalamic-pituitary-adrenal (HPA) axis responds more slowly. It releases cortisol, which helps the body sustain energy, control inflammation, and restore balance. To understand the biologic effects of stress and how pets may influence those effects, researchers needed to measure how both the SAM and HPA systems respond during and after stressful events. This involves tracking physiological indicators like heart rate, cortisol levels, and salivary alpha amylase, which reflect the activity of the two systems. Here’s how the stress test went: 44 people who had dogs were randomly selected to participate with or without their pet, going through a 15-minute stress inducer called the Trier Social Stress Test (TSST), the gold standard for triggering psychological stress in a lab setting. Researchers measured levels before, immediately after, and 45 minutes later to capture both the reaction and recovery. For 30 minutes, the subjects rested. Then came the instructions. “Write a speech about why you’re the best candidate for your dream job.” Moments later, they had to deliver that speech—on camera—while being silently observed and recorded by a panel of supposed behavioral experts in white lab coats, clipboards in hand. Next came the mental math under pressure. “Start at 2023 and subtract 17. Keep going, out loud, for five minutes.” After the test, they returned to a quiet room to recover. While there was no significant difference in self-reported anxiety, there was a profound

In the two decades since leaving the service, Williams’ journey has been marked by a series of setbacks and victories. Recently, she found a new source of support: a service dog named Montana from Freedom Service Dogs in Englewood, Colorado. The specially trained black Labrador does more than offer comfort. He senses her anxiety before it spirals. He applies pressure when she dissociates. He wakes her from nightmares. In public, he creates space between her and strangers. In private, he reminds her she’s not alone. “Montana has given me the opportunity to live again,” Williams says. “I can be a part of the world, a part of the community, and a part of life.” Williams is one of thousands of veterans living with PTSD who have experienced the life-changing impact of service dogs. It’s so profound that researchers at the Institute for Human-Animal Connection (IHAC) at the University of Denver’s Graduate School of Social Work (GSSW) are working to uncover the science behind it. To begin, they started with the basics: Do dogs affect how our bodies respond to stress in everyday situations? The biology of stress When we experience stress, our bodies turn on two important systems to help us respond and adapt to the situation. The sympathoadrenal medullary axis (SAM) is part of the sympathetic nervous system. This is the body’s fight-or-flight response. It reacts quickly to stress, releasing hormones

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UNIVERSITY OF DENVER MAGAZINE | AUTUMN 2025