Dogs Reduce Human Stress: New Biological Insights

A new study reveals that the stress relief humans experience from the companionship of dogs is biologically more complex than scientists previously imagined. In a 2022 survey of 3,000 American adults, more than one-third of respondents reported feeling "completely overwhelmed" by stress most of the time. At the same time, a growing body of research documents the negative health consequences of high stress levels, including increased rates of cancer, heart disease, autoimmune conditions, and even dementia.

Why Stress Management Is Important

As people's daily lives are unlikely to become less stressful anytime soon, simple and effective ways to mitigate its effects are needed.

Dogs: A Natural Solution

This is where dogs can help. As researchers at the Institute for Human-Animal Connection at the University of Denver in the United States, we study the effects of pets on their owners. Dozens of studies conducted over the past 40 years have confirmed that companion dogs help humans feel more relaxed. This would explain the growing phenomenon of people relying on emotional support dogs to help manage their daily lives. It has also been shown that dog owners have a 24% lower risk of death and are four times more likely to survive at least one year after a heart attack.

A Recent Study: More Complex Biological Effects

With a team of colleagues, we have just conducted a new study suggesting that dogs may have a deeper and more complex biological effect on humans than scientists previously thought. And this complexity could have profound implications for human health.

How Does Stress Work?

The human stress response involves a set of diverse physiological processes that are finely tuned and coordinated. Previous studies on the effects of dogs on human stress focused on one process at a time. For our study, we broadened our scope and measured several biological indicators of the body's state, also known as biomarkers, from the two main stress mechanisms in the body.

This allowed us to get a more complete picture of how a dog's presence affects stress in the human body. The stress pathways we measured are called the hypothalamic-pituitary-adrenal (HPA) axis and the sympatho-adreno-medullary (SAM) axis. When a person experiences a stressful event, the SAM axis reacts quickly, triggering a "fight or flight" response that includes an adrenaline surge and provides an energy boost to deal with threats.

What Our Study Measured

For our study, we recruited about 40 dog owners to participate in a standard 15-minute laboratory stress test. This test involves public speaking and doing mental math out loud in front of a panel of impassive people posing as behavior experts. Participants were randomly divided into two groups: those who had to come to the lab with their dog and those who had to leave their dog at home. We measured cortisol levels in blood samples taken before, immediately after, and about 45 minutes after the test, as a biomarker of HPA axis activity. And unlike previous studies, we also measured alpha-amylase enzyme levels in these same blood samples, as a biomarker of SAM axis activity.

Key Findings

As expected, consistent with previous studies, people accompanied by their dog showed lower cortisol peaks. But we also found that those with their dog experienced a significant spike in alpha-amylase, while those without their dog had virtually no response. The lack of response might seem positive. But in reality, a zero alpha-amylase response can be a sign of a dysregulated stress response.

This is often seen in people suffering from intense stress reactions, chronic stress, or even post-traumatic stress. This lack of response is caused by chronic or intense stress that can alter how our nervous system reacts to stressors. In contrast, participants accompanied by their dog showed a more balanced response: their cortisol levels didn't rise too much, but their alpha-amylase still activated. This shows they remained alert and focused throughout the test, then returned to a normal state in less than 45 minutes. That's the ideal timeframe for effectively managing stress. Our research suggests that our canine companions help us stay in a healthy stress response zone.

Dogs and Human Health

This finer understanding of the biological effects of dogs on human stress responses opens up exciting possibilities. Based on our study's results, our team has launched new research using thousands of biomarkers to deepen our knowledge of the biology behind how psychiatric service dogs reduce post-traumatic stress disorder in veterans. But one thing is already clear: dogs are not just good companions. They may well be one of the most accessible and effective tools for staying healthy in a stressful world.

Source: The Conversation