Dogs Help People Manage Stress Better Than Researchers Expected

In a 2022 survey of 3,000 U.S. adults, more than a third of respondents reported feeling “completely overwhelmed” by stress on most days. At the same time, a growing body of research is documenting the negative health effects of high stress, including increased risks of cancer, cardiovascular disease, autoimmune disorders, and even dementia.

Given that it is unlikely that people's daily lives will become less stressful any time soon, simple and effective ways to mitigate these effects are needed.

Dogs can help here.

As researchers at the Institute for the Human-Animal Bond at the University of Denver, we study the influence of companion animals on their owners.

Dozens of studies over the past 40 years have confirmed that pet dogs help people feel more relaxed. This explains the growing phenomenon of people relying on emotional support dogs to help them cope with everyday challenges. Dog owners have also been shown to have a 24% lower risk of dying and are four times more likely to survive at least a year after a heart attack.

Now, new research that I conducted with a team of colleagues suggests that dogs may have a more profound and biologically complex effect on humans than previously thought. And this complexity could have serious implications for human health.

How Stress Works

The human stress response is a finely tuned and coordinated set of different physiological pathways. Previous studies of the effects of dogs on human stress have focused on only one pathway at a time. In our study, we took a broader approach and measured multiple biological indicators of body condition (biomarkers) from both of the body’s major stress systems. This allowed us to get a more complete picture of how the presence of a dog affects human stress.

The stress systems we measured were the hypothalamic-pituitary-adrenal (HPA) axis and the sympathoadrenal (SAM) axis.

When a person is faced with a stressful event, the SAM axis reacts quickly, triggering the fight-or-flight response, which includes a release of adrenaline and a surge of energy to help cope with threats. This response can be measured by levels of the enzyme alpha-amylase.

At the same time, but slightly more slowly, the HPA axis activates the adrenal glands to produce the hormone cortisol, which helps cope with threats that last for hours or even days. If all goes well, once the danger has passed, both axes return to a calm state.

Although stress can be an unpleasant feeling, it is important for human survival. Our hunting ancestors had to respond effectively to acute stressful situations, such as an animal attack. In such cases, overreacting or underreacting could be equally dangerous. Staying in the “optimal zone” of the stress response maximized the chances of survival.

More than just cortisol

Once cortisol is released by the adrenal glands, it eventually ends up in saliva, making it a useful biomarker for tracking responses. As a result, most studies on the effects of dogs on stress in humans have focused only on salivary cortisol.

For example, several studies have shown that people exposed to a stressful situation had a lower cortisol response when they had a dog nearby than when they were alone—and even lower than when they had a friend nearby.

While these studies showed that the presence of a dog can reduce cortisol levels during a stressful event (indicating that a person is calmer), we suspected that this was only part of the picture.

What our research showed

In our study, we invited approximately 40 dog owners to complete a 15-minute standard laboratory stress test involving public speaking and verbal counting in front of a panel of neutral-faced people posing as behaviorists.

Participants were randomly assigned to one of two groups: one brought their dog to the lab, the other left it at home. We measured cortisol in blood samples taken before, immediately after, and approximately 45 minutes after the test as a marker of HPA axis activity. Unlike previous studies, we also measured levels of the enzyme alpha-amylase in the same blood samples as a marker of SAM axis activity.

As expected, people with dogs had a smaller spike in cortisol. But we also found that people with dogs had a clear spike in alpha-amylase, while people without dogs had almost no response.

The lack of response may seem like a good sign, but in fact, a flat alpha-amylase response can be a sign of stress system dysfunction, often seen in people with high stress levels, chronic stress, or even post-traumatic stress disorder (PTSD).

In contrast, participants with dogs showed a more balanced response: their cortisol didn’t rise too high, but their alpha-amylase was still activated. This shows that they were alert and engaged during the test, and were able to return to normal within 45 minutes. This is the “sweet spot” for effective stress management. Our research suggests that dogs help us stay in a healthy stress response zone.

Dogs and Human Health

A deeper understanding of the biological effects of dogs on human stress responses opens up exciting possibilities. Building on our findings, our team has launched a new study using thousands of biomarkers to further explore how psychiatric service dogs help reduce PTSD in military veterans.

But one thing is already clear: dogs are more than just good company. They can be one of the most accessible and effective tools for staying healthy in a stressful world.