Dog companions linked to healthier stress regulation during high-pressure situations

Stress can be harmful to both your body and mind, but your dog may be able to help.

Acute stress is more than just a passing feeling of nervousness. The hypothalamus pituitary adrenal (HPA) axis and the sympathoadrenal medullary (SAM) axis are two important systems that are triggered when the body perceives a threat, such as public speaking or an argument. These systems trigger a cascade of hormonal and nervous system responses, including spikes in cortisol and heart rate, to help the body react to immediate danger. Although the stress response is beneficial in brief instances, studies reveal that improperly controlled stress, whether too strong or too mild, might raise the risk of long-term health issues like heart disease and mental health disorders.

In light of rising global stress levels, scientists are actively seeking simple, non-drug interventions that can help regulate how the body responds to stress. Many people turn to activities like meditation, exercise, or time in nature to decompress. However, another easy and well-known source of support is becoming more and more popular: our pets, particularly dogs. The idea that a dog’s presence can influence biological markers of stress has become a serious topic of investigation in psychology and health research.

Prior research has indicated that dogs may assist lower blood pressure or heart rate during stressful situations, as well as on subjective distress. However, most of this research has focused on self-reported measures or limited biological indicators. Now, a new study published in Stresses takes this a step further by examining how pet dogs influence the body’s full biological stress response, across both major stress systems. Research shows that just seeing a familiar dog can help the body react to abrupt stress in a more balanced and healthy way, even if the person does not immediately feel less anxious.

What the researchers did: A stress test with and without dogs

To examine the effect of dogs on biological stress responses, researchers at the University of Denver conducted a randomized controlled trial using one of the most well-established psychological stressors: the Trier Social Stress Test (TSST). The TSST reliably induces acute stress by combining social evaluation and unpredictability. Participants are asked to deliver an impromptu speech and perform mental arithmetic in front of an unresponsive panel, while being filmed. This setup has been shown to reliably activate both the HPA axis (measured through cortisol) and the SAM axis (measured through alpha-amylase and heart rate).

In the study, healthy adult dog owners were randomly assigned to one of two conditions. One group completed the TSST with their pet dog present, while the other underwent the same stress test without their dog. Significantly, the dogs were not therapy animals; rather, they were common pets that the participants had become used to. The researchers wanted to test the real-life effect of everyday pet companionship rather than trained support animals.

To capture the full spectrum of stress responses, the team used a combination of self-report and physiological measures. Participants rated their anxiety using the State-Trait Anxiety Inventory (STAI), a validated questionnaire commonly used in psychological research. Heart rate, plasma cortisol levels, and salivary alpha-amylase, a lesser-known biomarker associated with the SAM system were all examined consecutively. These biomarkers were assessed at three time points: before the stressor, immediately after, and 45 minutes into recovery.

Key findings: Dogs reduced cortisol spikes and heart rate increases

The results showed that the presence of a pet dog had a measurable impact on biological stress responses. Participants accompanied by their dogs experienced significantly lower increases in heart rate during the stress test compared to those without their dogs. On average, the dog group’s heart rate rose by about 14.6%, while the no-dog group saw an increase of nearly 26.7%. This suggests that the dogs acted as a buffer against the cardiovascular arousal typically triggered by social stress.

A similar pattern emerged with cortisol, the primary stress hormone released by the HPA axis. Participants with their dogs had a 30% cortisol spike, compared to over 50% in the no-dog group. Importantly, cortisol levels in the dog group returned to baseline more quickly during the recovery period, suggesting not only a lower stress peak but also faster physiological recovery.

Interestingly, both groups reported similar increases in subjective anxiety, despite the clear biological differences. This mismatch between how people feel and how their bodies react has been documented in other stress studies, and suggests that dogs may help regulate physiological stress even if they don’t reduce the person’s perceived stress in the moment. In other words, even if you may still experience anxiety, having your dog at your side helps to maintain a more balanced balance of hormones and the heart.

The SAM and HPA systems: Why a balanced stress response matters

When we experience stress, two primary systems in the body work in tandem to help us cope: the sympathoadrenal medullary (SAM) axis and the hypothalamic–pituitary–adrenal (HPA) axis. The SAM system activates rapidly, increasing heart rate and blood pressure through the release of adrenaline and noradrenaline. This is the body’s first wave of defense, designed to respond immediately to threat. Shortly afterward, the HPA axis kicks in, releasing cortisol, which helps the body maintain energy and restore balance once the stressor has passed.

A dysregulated reaction, whether too strong or mild, can be an indicator of poor stress health even if both systems are necessary. Exaggerated reactivity, such as sky-high cortisol or sharply elevated heart rate, has been linked to cardiovascular disease, immune dysfunction, and anxiety disorders. In contrast, unhealthy physical and mental consequences have also been linked to muted reactions, particularly in SAM indicators like salivary alpha-amylase. Ideally, both systems should respond proportionately and recover efficiently.

In this study, only participants with their dogs showed a significant increase in salivary alpha-amylase, suggesting a more active and healthy SAM axis response. Those without dogs exhibited a “flat” response, meaning their bodies failed to engage this stress pathway effectively. While the exact implications of this are still under study, a responsive but not excessive activation of both SAM and HPA systems is increasingly recognized as a sign of physiological resilience. The dog group, in this case, showed that kind of balance.

Blunted stress response in the control group may be a red flag

When people did the stress test without their dogs, their alpha-amylase hardly budged. In other words, this SAM marker showed little to no increase during the acute stressor. While it might seem beneficial to have a “calm” biological reaction, this flattened response pattern is not considered healthy. In fact, research suggests that a lack of reactivity may indicate a stress system that is worn down or dysregulated, particularly after long-term exposure to chronic stress.

Blunted stress responses have been observed in individuals with post-traumatic stress disorder (PTSD), major depression, borderline personality disorder, and chronic fatigue syndrome. They have also been connected to decreasing immune system health, mental decline, and increased physical limitations in age. The finding that participants without their dogs mirrored this kind of biological profile raises concerns, even though they were healthy at baseline. It suggests that their stress systems may not be operating optimally under pressure.

According to the study’s authors, the no-dog group’s muted reaction might have been caused by the larger environment, such as social isolation or stress from the COVID-19 outbreak, however the outcome is nonetheless noteworthy. It emphasizes the importance of studying under-reactivity as well as over-reactivity in stress research. Psychological stress is sometimes presented as something that must be decreased, but in the truth, a responsive and well-regulated system is healthier than one that does not respond at all.

Why dogs might help: Beyond emotional comfort

While many pet owners would agree that their dog makes them feel better, this study suggests that the benefits may go beyond emotional support. Physiological markers showed that participants with dogs had more balanced responses across both major stress systems, even though they reported feeling just as anxious as those without dogs. This disconnect highlights an important idea in stress science: the body can benefit from non-conscious or automatic regulation, even when subjective feelings don’t change.

Researchers suggest that simply being near a familiar dog may engage regulatory mechanisms that help the nervous system manage stress more effectively. For example, previous studies have linked pet interaction to changes in oxytocin, a hormone associated with bonding and calm. According to other beliefs, even if we are not completely aware of it, dogs may serve as a social buffer that lessens the feeling of being judged or alone during stressful situations.

Another possibility is that a familiar dog subtly shifts the person’s attentional focus or vigilance. In the high-pressure context of the stress test, the presence of a trusted pet may have provided a grounding or stabilizing effect, giving the body a sense of safety. Whether through hormonal shifts, social context, or nervous system feedback, the findings support the idea that dogs influence our biology in meaningful ways, even when our conscious mind is still under pressure.

Study limitations: Who was studied, and what still needs to be tested

While the findings are compelling, the study has several important limitations. The participant pool was relatively small and primarily composed of white, middle-aged women, which limits how widely the results can be generalized. Stress physiology can vary by age, sex, and race due to differences in hormone profiles, social experiences, and cultural stressors. As a result, it’s unclear whether similar effects would be observed in men, younger individuals, or more diverse populations.

The timing of the study may also have played a role. Data collection occurred during the COVID-19 pandemic, a period when many people experienced heightened social isolation and chronic stress. This broader context could have influenced baseline stress levels or contributed to the blunted alpha-amylase responses seen in the no-dog group. Although the researchers attempted to control for known variables, pandemic-related stress wasn’t explicitly measured.

Importantly, the study focused only on acute stress responses in healthy adults. It remains unknown how pet companionship might influence stress regulation in individuals with clinical diagnoses such as anxiety disorders, PTSD, or chronic health conditions. Interaction with pets may benefit these groups more or less, and they may respond differently to stress. Broader, more inclusive studies are needed to clarify who stands to gain the most from these effects.

Future directions: Comparing pets, therapy dogs, and social support

One key question for future research is whether the calming effects observed in this study depend on the familiarity of the dog. Would a therapy dog or stranger’s pet offer the same physiological benefits? Or is there something unique about a personal, ongoing human–animal bond that moderates stress regulation? Studies comparing owned pets vs. therapy animals could help disentangle the role of relationship closeness in stress buffering.

Another interesting direction would be to compare pet companionship with human social support, such as the presence of a close friend or family member during a stressor. While previous research suggests that dogs can be even more effective than people in certain stress contexts, there hasn’t been a direct, head-to-head comparison using the full range of physiological biomarkers like alpha-amylase and cortisol.

Researchers could also expand this work to explore whether similar effects are observed with other animals, such as cats or small mammals. Additionally, most studies to date, including this one, focus on short-term stress responses. It remains unclear whether regular exposure to a pet leads to sustained improvements in health, reduced inflammation, or better cardiovascular outcomes over time. Longitudinal studies could shed light on whether pet ownership truly promotes long-term physiological resilience.

Bottom line: Your dog might be keeping your stress response in check

This study adds new evidence to the growing body of research suggesting that pet dogs may play a regulatory role in how our bodies handle stress. By examining markers from both the HPA and SAM axes, the researchers found that the presence of a dog during an acute stressor supported a more balanced and healthy physiological response. This calming effect is linked to better mental and physical health, as demonstrated by smaller heart rate spikes, lower cortisol levels, and more balanced alpha-amylase activation.

It’s important to emphasize that having a dog isn’t a substitute for mental health treatment or medication when needed. However, for everyday stressors, pet companionship may offer a simple, accessible intervention that helps people stay physically and emotionally regulated. Even when people don’t feel calmer, their bodies may still benefit from the presence of a trusted animal.

These findings also have broader implications for how we think about human-animal relationships. Rather than viewing pets solely as sources of emotional comfort, this research suggests they may serve as biological co-regulators, helping us maintain internal balance in the face of life’s challenges. As stress-related health problems continue to rise globally, understanding the subtle but powerful effects of pet companionship could inform new approaches to public health and prevention.