February 13, 2025, 9:37 am | Read time: 5 minutes
Stress can make you ill in the long term. This is true for humans but also for animals. The link between stress and cancer has long been the subject of discussion and research. But what is the truth of this assumption, and what does it mean for the health of dogs?
Cancer is a leading cause of death in dogs – but is it caused by stress? Almost 50 percent of all four-legged friends over the age of 10 develop cancer.1 “The reality is that an increasing number of dogs are euthanized prematurely due to cancer. There are two important reasons for this,” explains dog psychologist Marc Ebersbach in an interview with PETBOOK. Firstly, dogs, like humans, are getting older, which means that the risk of cancer increases with age.2
“Additionally, it’s observed that dogs today face rising levels of stress, which, for instance, leads to increased cortisol in their bloodstream,” explains the dog expert. However, what is causing such high levels of stress in dogs?
“Many owners try to teach their dogs what is expected of them sometimes using brutal methods”
“There are many reasons for the increasing stress levels of our dogs.” In the past, dogs tended to be kept in rural areas and were generally more relaxed when accompanying people. But that has changed dramatically, explains Marc Ebersbach.
“Nowadays, many dogs reside in urban environments and are regarded as social companions with high expectations placed upon them,” summarizes the dog psychologist. “As not every dog is naturally suited to this role, many owners try to teach their dogs what is expected of them, sometimes using brutal methods.”
Ebersbach reveals that the dog professional sometimes witnesses disturbing scenes. “When I walk through the streets and witness how some dogs are disciplined by their owners and the immediate fear it instills in them, it’s deeply troubling.”
The Thing with Stress Hormones
Stress is not just an emotional feeling for dogs but a physical and psychological reaction to stressful or challenging situations, the expert explains. It is a natural mechanism of the body that reacts to possible threats or high demands in order to ensure survival. This is why the body releases stress hormones in such situations.
The resulting stress hormone cortisol is known to build up in the body faster than it is broken down again. The rapid increase in stressful situations and the slower reduction afterward could lead to dogs with chronic stress having permanently elevated cortisol levels. This, in turn, can have negative effects on health. Among other things, a weakening of the immune system and an increased risk of diseases such as cancer – according to the theory.
Is Stress Carcinogenic in the Long Term?
But what does science say? Veterinarian and scientist Dr. Vanessa Herder explains in a PETBOOK interview that this question is not so easy to answer. A connection between stress and tumor diseases has been discussed again and again for decades. However, “the scientific data in dogs and humans is not conclusive on this issue. In various rodent models, research has shown that stress accelerates the progression of cancer.”
While the bulk of research has centered on human subjects, nevertheless, there are studies that show “that avoiding stress in the sense of reducing elevated inflammatory parameters and cortisol levels, e.g., by administering medication, can save lives in cancer patients – humans and laboratory animals.”
“Stress Is Not Always Negative”
In scientific studies, the focus is on people, explains Dr. Herder. “It is often not possible to arrive at clear results due to the diversity of the patients studied. Using rodents under standardized conditions, it was possible to show that stress can cause the growth of cancer and metastases.”
These studies showed that hormonal, cellular, and molecular mechanisms play a decisive role, Herder concludes. But stress is also relative, the veterinarian concedes. “Stress is not always negative. Over a short period of time, it helps the body to adapt.”
However, if the intensity, duration, and type of stress trigger become too strong, it can have a toxic effect. This can then increase the risk of illness. “The harmful effects of intensity and duration are very individual for each animal and each person. What is extremely stressful for one person can be completely stress-free for another.”
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However, it must also be said that the scientific data and studies on this topic are still very limited, says Dr. Vanessa Herder. Although dogs and humans are both mammals and are very similar in many biological processes relating to inflammation and stress, they are not identical. Therefore, it’s crucial to avoid drawing direct parallels between humans and dogs. As psychosomatic stress is not the only factor in cancer, this is a very complex area.
“You have to bear in mind that nutrition, viral infections, environmental factors, genetic conditions, and much more also have an influence on the development and progression of cancer.”
Nevertheless, Dr. Herder asserts one key point: “In humans, it has been shown that good stress management has a positive influence on the course of the disease in cancer patients. This may also hold true for dogs. However, many questions remain unanswered, necessitating further research, concludes Dr. Herder.