Mind-body connection in animals

If you’ve ever witnessed the decline of a pet shortly after the loss of another, you’ve seen the mind-body connection in action. Here’s a closer look at this incredible phenomenon.

Rico and Pablo, two jet-black cats, had lived together as the closest of companions for their entire lives – all 16 years. Both had been exceptionally healthy up until the day that Pablo began to show problems passing urine. After several tests and x-rays, it was discovered that Pablo had inoperable bladder cancer. With no treatment available, his discomfort quickly worsened, and euthanasia seemed the most humane option.

Rico was never the same. Without his companion, he was simply inconsolable; he meowed 20 hours a day. In the ensuing months, his health deteriorated. He lost weight and lacked coordination, and tests revealed serious blood cell abnormalities. It seemed that Rico’s once robust health was ravaged by his grief over losing Pablo. Within a short time, Rico’s illness led to his demise.

In the past few decades, a rapidly expanding body of clinical and experimental evidence — on humans and other animals — supports a strong interrelationship between emotions and bodily health processes.

Uniting the mind and body

As late as the mid-1900s, scientists believed that the various body systems operated independently of one another. The breakthrough in our understanding of the interaction of mind and body came when researchers discovered the mechanisms by which the different systems of the body communicate with one another. Studies revealed that a group of chemical messengers, called neuropeptides, transmit messages from body system to body system. This body-wide communication network allows the systematic coordination necessary for effective responses to environmental challenges. Moreover, neuropeptides were found to play a large role in emotions and feelings.

Mind-body connection in action

Scientific evidence for the functional link between the mind and body began with the finding that the brain had great influence over the immune system. Using Pavlov’s method of classical conditioning by which he trained his dogs to associate the sound of a bell with the presentation of food, scientists showed that the immune system could be trained in the same way. If a neutral stimulus, such as the sound of a bell, was paired with an immune system stimulant, eventually the presentation of the bell alone caused the same immune response. This was a revolutionary discovery, for it showed for the first time not just that the brain communicated with the immune system, but that there was now a solid scientific basis for the connection of the mental and physical aspects of living animals. Many additional studies followed, confirming the constant and extensive flow of communication between the brain and body systems.

Some of the most dramatic evidence demonstrating the connection between mind and body was the discovery that animals could learn to exert mental control over many basic body processes that are not normally under conscious control. Quite incredibly, cats, rabbits and rats were able to gain control of their own blood pressure, rate of kidney filtering, and intestinal contractions. By showing that simple conscious thoughts could command major changes in the physiology of the body, these studies erased all doubt that the mind was intimately connected to the functions of the body.

Emotions and body health

Emotional states have been found to be associated with a wide array of health effects, ranging from immune system function and cancer to cardiovascular and renal disorders.

Shawnee, a five-year-old female Labrador was suffering from a terrible gastrointestinal upset. Her human companion revealed that the home was in emotional turmoil, with teenagers fighting and yelling. Shawnee would become very upset and run into another room to escape the discord. Her health problems began when the fights first started. Similarly, Brittany, a young terrier mix, had been caught in the middle of volatile husband-wife tensions and arguments in her house. As a result, she began vomiting frequently. And Duncan, another Labrador, reacted to arguments in his home by having allergy break-outs.

Many scientific studies have also shown how anxiety and fear are associated with ill-health effects. Emotional stress can suppress the immune system, allowing more frequent and severe infections. High blood pressure, increased incidence of cancer, gastrointestinal diseases, urinary problems, asthma, urinary blockages and allergies have all been found to be connected to fear or anxiety.

Loneliness seems to be one of the most important emotions. Being left alone at home while human companions are vacationing has led some animals to develop skin rashes, stomach disorders and bladder conditions.

Grief and depression can also strongly influence health. Boomer was a robustly healthy black Labrador whose human companion, David, was dying of AIDS. Boomer showed no problems until a few days before David died. Boomer became depressed and stopped eating. Following David’s death, Boomer’s condition deteriorated rapidly, and soon he too was dead. By all appearances, Boomer’s physical condition resulted from his emotional distress and grief.

Atherosclerosis, cardiac disease, decreased reproductive functions, and other bodily changes have also been linked to a variety of emotions in animals.

Health benefits of positive emotions

Interestingly, not all emotional stress is associated with detrimental health changes. In some experiments, stress-related effects have been beneficial to health. Stress is occasionally found to have a protective effect against infection and can slow the rate of cancerous tumor growth. Whether the health effects of emotions are undesirable (the vast majority) or beneficial (less common), they all represent an interaction between the mind and body.

The mind-body effect that one might expect to spark the most interest among medical researchers is the influence of positive emotions on health. If the negative (unpleasant and stressful) emotions are so extensively associated with adverse health, would it not be a logical assumption – and a critical area for research – that positive emotions would promote health? Curiously, there has been little study in humans (and even less in animals) regarding the beneficial health effects of positive emotions.

Preliminary research with dogs has recently shown an intriguing association between positive emotional states and improved health. The studies have looked at the devastating disorder of canine bloat, in which the dog’s stomach quickly fills with air and, if not recognized and treated quickly, will rapidly progress to death. A consistent finding in these studies was that there was a decreased risk of bloat in dogs that owners judged to be “happy”. In one study, the risk in happy dogs was decreased by an astounding 78 per cent, when compared with dogs not characterized as happy. This association does not prove that the emotional state is the cause of the improved health status, but such evidence certainly warrants research to investigate the potential for positive emotions to promote good health.

A placebo effect in animals?

Although it seems odd that animals would have a placebo effect — after all, how could they know what the treatment is for and how could they expect to get better? – many studies have confirmed that animals have quite powerful placebo effects. For example, one study which examined the effects of a new pain-relieving drug on dogs with arthritis, relied on a precise measurement of the amount of weight the dog put on its arthritic leg before and after the real drug and a placebo drug. Amazingly, more than 50 per cent of the dogs receiving the placebo drug showed a positive response and had improved use of the affected leg.

The effect of the loving touch

Offering evidence of a different type of mind-body interaction is a group of intriguing studies which have shown that the gentle touch of a human being can exert strong physiologic and health effects in animals. In dogs and horses, petting by a human is associated with dramatic decreases in heart rate. Human contact elicits major changes in blood pressure and coronary artery blood flow in dogs. Farm animals showed positive effects with gentle human contact. Dairy cattle handled gently had increased milk production and female pigs showed increased reproductive fertility when simply given the company of a person.

Acknowledging the evidence

An enormous amount of evidence now exists to show that the mind and body of animals are deeply and extensively interconnected. It appears that all body systems of the animal body communicate with and influence one another. Emotions and thoughts exert a profound effect on the course and outcome of health and disease states. In all, it now appears that all known aspects of the physical functioning of the animal body are affected by the mind. Medical care, to be complete and effective, must take into full account the mind, emotions and feelings of animals. Medicine can only succeed if it views the animal as a mind-body entity. The mechanistic approach of treating physical diseases with drugs and surgery – like some kind of car repair shop – should now be discarded as an outmoded, and substandard, approach to healing God’s creatures.


Franklin D. McMillan, DVM has been the director of well-being studies at Best Friends Animal Society since 2007. Prior to this he was in private practice for 23 years as well as clinical professor of medicine at the Western University of Health Sciences College of Veterinary Medicine. Dr. Frank is board-certified in the veterinary specialties of small animal internal medicine and animal welfare. His research concerns animal quality of life and the mental health and emotional well-being of animals who have endured hardship, adversity, and psychological trauma — the goal of these studies is to better understand the effects of trauma and to develop new therapies to restore to these animals a life of enjoyment rather than one filled with fear and emotional distress. Dr. Frank lectures worldwide and has published dozens of scientific journal articles and is the author of the textbook Mental Health and Well-Being in Animals, and a book for the general public titled Unlocking the Animal Mind.