Stress in Cats: Causes, Effects, Prevention.

This time, a bit about stress — how it is commonly understood and what it really is, why it is so dangerous. The physiology of stress is the same for us and for our feline companions.

What is stress?

The common understanding of stress — that a cat (or a human) is nervous or agitated — has little to do with what stress truly is. This simplification likely comes from the fact that sometimes we clearly see symptoms of stress and associate them with nervousness. However, stress is something that happens on a physiological level, without engaging our will or conscious ability to control its course. Stress is the physiological response of the body to changes in the surrounding world — not only negative ones, but also positive ones. Every change requires some adaptation, every change is a challenge, putting the body in full readiness for various actions. On the physiological level, even a positive change can become the beginning of a chain of destructive processes.

Stress is therefore something that happens outside our control, whenever the body perceives certain conditions as more or less threatening. What’s more, this happens regardless of whether the threat is real or not. On the metabolic level, without our will and regardless of training, regulatory mechanisms activate to prepare us for various possibilities. Training helps only to modify behavior — to not react immediately in the way the body dictates. To illustrate: when we watch “Jaws,” we know the shark won’t eat us, we don’t run away from the TV, we don’t call for help, we don’t look for a place to hide — yet our heart races, adrenaline levels rise, pupils dilate, blood pressure increases. Even though we appear calm, our body is in a state of stress, and it hardly matters that we know the threat isn’t real. The same applies to our cats — a cat that is quiet, sleeping, or seemingly relaxed may still be experiencing chronic stress.

Even scientists struggle to define stress :)

"Stress is not what happens to you, but how you react to what happens to you."

"Stress is a nonspecific response of the body to any demands placed upon it."

"Stress is the body's reaction in the form of mobilizing energy to overcome various obstacles, barriers, or demands, regardless of whether pleasant or unpleasant feelings accompany it. It is a nonspecific reaction, meaning its type does not depend on the factor that triggers it."

What causes stress?

Every change is a source of stress, regardless of whether it is beneficial or not. Our bodies do not distinguish between “good” and “bad” stress. Below are examples of events that happen to most of us from time to time, along with the stress level they induce — that is, how strong the physiological response is across the nervous, hormonal, and immune systems. The scale ranges from 1 to over 100 points, with the strongest reaction exceeding 100.

Death of a life partner – 119

Divorce – 96

Imprisonment – 63

Death of a close family member – 63

Personal illness – 53

Wedding – 50

Job loss – 47

Retirement – 47

New family member – 39

Large loan – 31

Conflict with boss – 23

Moving to a new home – 20

Vacation – 13

Christmas – 12

Minor legal violation – 11

Cats experience similar situations: arrival of a new cat, moving homes, disappearance of a bonded companion (cat/dog/human), poor relationships with another cat (poor even when there are no open conflicts), arguments between owners, doors being closed to rooms that were previously accessible, or subtle factors that owners struggle to identify — such as the smell of another cat in the hallway, a cat walking outside the window, or environmental elements like flapping fabric or a scarecrow. Every time the cat sees “the stranger,” its body responds, putting it in full alert — even if the stranger is behind glass.

What happens to a cat under stress?

What happens when a cat encounters a change it cannot cope with, or when its environment contains a factor it cannot manage — such as a neighbor’s cat walking outside the window, a new household member, or any other disruption to its orderly world?

In simplified terms, we can distinguish four phases of reaction to a sudden stimulus:

1. A stimulus detected by one of the five senses is received by the brain (e.g., a strange meow).

2. The brain classifies the stimulus as “threatening” or “non-threatening.” If non-threatening, the reaction ends here. If perceived as concerning, the brain immediately activates the nervous and endocrine systems to prepare the body for fight or flight.

3. The body remains in a state of readiness and alarm until the threat is recognized as gone.

4. The body returns to equilibrium once the threat disappears.

Physiology of stress

Three systems are involved in the physiological stress response: the nervous system, the endocrine (hormonal) system, and the immune system.

The most relevant part of the nervous system is the autonomic nervous system — fully “automated,” innervating internal organs. It consists of two branches: the sympathetic (responsible for arousal) and the parasympathetic (responsible for calming and relaxation). The sight of a cat outside the window triggers an immediate, unconscious sympathetic response, sending strong activating signals to internal organs, endocrine glands, and strongly inhibiting the immune system (immunosuppression).

When a cat perceives a threat, the sympathetic system releases large amounts of adrenaline and noradrenaline from nerve endings, and simultaneously stimulates the endocrine system to release additional hormones — adrenaline, noradrenaline, and cortisol. These hormones strongly stimulate the body, and cortisol has a particularly harmful effect on the immune system.

What happens in the cat’s body when it sees an intruder outside the window? Most of these reactions are invisible — the cat may appear calm!

• dilated pupils;

• accelerated heart rate;

• blood vessel constriction;

• increased blood pressure;

• elevated blood glucose;

• elevated blood lipids;

• increased muscle tension (especially neck and legs);

• stimulated intestinal activity;

• stimulated bladder activity;

• bronchodilation;

• shallow, rapid breathing;

• release of substances that accelerate blood clotting.

All these changes occur automatically, every time the cat encounters something disturbing — several or even dozens of times a day. If the stressor is another cat or a household member, the frequency may be even higher.

Adrenaline is a “first-line” hormone and drops quickly. Noradrenaline persists longer, meaning its stimulating effect continues even after the intruder disappears.

Cortisol is the most dangerous hormone released in response to change. In natural amounts, it is essential for maintaining homeostasis — regulating glucose and lipid metabolism, and sodium-potassium balance (kidney function!). Excess cortisol causes potassium loss, elevated glucose and lipid levels, and severely impairs immune function. Cortisol levels also rise dangerously when the body is deprived of sleep.

Below are data showing how quickly various substances are released — explaining why the stress response is unavoidable and cannot be trained away.

With long-term exposure to stressors (like a terrible boss), we may get used to the symptoms — we stop noticing our racing heart — but the heart still races. Just like we stop hearing the tram outside, but it is still there. We may talk to our boss with a racing heart and appear calm, but our body pays the price.

I describe all this because stress in cats is still underestimated. When mysterious, recurring illnesses appear, besides basic tests, I always ask owners to examine the cat’s life — whether it is truly free from overwhelming challenges. This does NOT mean you don’t love your cat. We all try to give them the best conditions. It simply means that sometimes our idea of “best conditions” does not match the cat’s.

You cannot get used to a stressor, nor can you learn it away — the body will always react the same way. I am talking about physiology — externally it may seem that we have adapted, that we know the boss won’t kill us, just as the cat knows the other cat is behind glass. But physiology does its job — because this mechanism has worked for millions of years of evolution.

Under normal conditions, when the stressor disappears or is recognized as harmless, the parasympathetic system activates, calming the body. Nerve endings release acetylcholine, which:

• dilates blood vessels,

• lowers blood pressure,

• slows heart rate,

• reduces the strength of heart contractions,

• constricts pupils.

Everything has passed — time to stretch and return to favorite activities, maybe take a nap?

Effects of chronic stress

Stress itself is not bad — it is a normal adaptive mechanism. Without stress, there is no life :) Under normal conditions, when the stressor disappears, the cat’s body returns to balance, and the cat can learn how to behave if the situation repeats. The problem begins when the stressor becomes a constant element of the cat’s life, when one stressor follows another, exceeding the cat’s adaptive capacity. The body remains in a hormonal rollercoaster, constant arousal, and without periods of relaxation, transitions into exhaustion — leading directly to illness, and sometimes death.

The effects of chronic stress can be very serious:

1. Prolonged elevated heart rate, constricted vessels, and blood pressure spikes can lead to chronic hypertension and serious heart disease, including cardiomyopathy.

2. Intestinal stimulation often leads to “nervous bowel,” poor absorption, deficiencies, and unexplained diarrhea or constipation.

3. Similar stimulation affects bladder and urethral muscles — excessive contractions lead to narrowing of the urethra, urine retention, and inflammation of the lower urinary tract.

4. Cortisol raises cholesterol and glucose levels, leading to diabetes, atherosclerosis, cardiovascular and respiratory diseases, clotting disorders, hypertension, and cardiomyopathies.

5. Chronic stress impairs thyroid function — often causing hyperthyroidism, which quickly damages the heart.

6. Weight gain — rarely associated with stress — is often its direct result. Cats may eat little but still gain weight due to disrupted fat–glycogen metabolism and water retention caused by high cortisol.

7. Cortisol causes shrinkage of lymphatic organs (thymus, spleen, lymph nodes), drastically reducing white blood cell count — leading to immune collapse and disease.

8. High adrenaline and cortisol reduce estrogen and progesterone production — leading to infertility or inability to maintain pregnancy.

9. Another consequence of immune dysfunction is autoimmune disease — including inflammatory joint disease, where the body attacks synovial membranes, causing destructive inflammation.

It is not easy to recognize a cat living in chronic stress — we expect such a cat to be nervous, aggressive, overly reactive. If so, we notice the problem. Worse is when the cat tries to “wait out” discomfort — pretending nothing is happening, sleeping excessively, grooming excessively (sometimes to bare skin), eating more but moving little, lying down immediately after meals in a state of vigilant pseudo-sleep. They may have recurring intestinal issues, bladder inflammation, watery eyes, allergies, intolerances. Because they do not move or play — they gain weight. Owners often notice the problem only during routine exams — discovering diabetes, kidney disease, or cardiovascular issues.

How to prevent chronic stress?

How can we protect our cats from chronic stress? As mentioned, this type of stress is dangerous because single changes are unavoidable — and if followed by time to recover, the body can cope. We must watch out for factors that constantly keep cats in a state of alert, regardless of whether we consider them justified.

First, we must ensure the cat’s environment is rich and full of “safe havens” — from the cat’s perspective. More about this in the section “A Cat-Friendly Home.” Also, no matter how much we love cats, we must remember they are not social animals. They do not thrive in large groups. They lack stable social structure, so “the other cat” is always a potential threat. Two cats are usually manageable. Introducing a second cat should be preceded by careful analysis of the home and whether it provides enough territory. A third cat is a major challenge — I rarely place cats in homes that already have two.

Psychological balance is supported by an orderly life. Cats are creatures of ritual — they love checking whether everything is in its place. This does not mean they dislike small changes — adding a box or a small piece of furniture is often delightful. But major changes — guests, new cats, babies, moving — are huge stressors. Poor bonding with another cat is a source of chronic stress. A neighbor’s dog leaving scent marks at the door, or a cat sitting outside the window staring in — if this happens regularly, it becomes chronic stress.

Breeders often have more cats. I keep 5–6 females together. Anyone who visits quickly understands how this is possible — and must ask themselves whether they could live among scratching posts, hammocks, tunnels, toys everywhere, and multiple litter boxes. This is the price of peaceful coexistence — hopefully with minimal stress. Not none — because motherhood, or another cat’s motherhood, is stressful too :)

Cats are wonderful but extremely delicate creatures. They dislike showing weakness — evolution prepared them to rely only on themselves. Their signals of discomfort are subtle. We often misinterpret them — for example, seeing two cats squeezed into one bed and assuming they love each other. In reality, neither is comfortable — they squeeze together because the owner bought only one bed. A simple experiment with more beds shows that adult cats NEVER sleep together in one bed unless forced by lack of space. They may lie close, but touching happens only when both insist on staying in a spot too small to separate. Entering a bed where “the other cat” already lies — and where stretching comfortably is impossible — does not reduce daily stress.

Learning their mysterious world is worthwhile — nothing brings more joy than a happy, relaxed, healthy cat.

Dorota Szadurska, COAPE Behaviourist Supervisor
Graduate in Advanced Diploma in Feline Behaviour Management (Level 5, UK)
Graduate of Animal Psychology, Polish Academy of Sciences, Warsaw
Member of The International Society of Animal Professionals
Member of The International Association of Animal Behavior Consultants

Dorota Szadurska, COAPE Behaviourist and Studium Kot
Graduate of Animal Psychology, Polish Academy of Sciences, Warsaw
Graduate of Companion Animal Care and Breeding, Wrocław University of Environmental and Life Sciences
Member of The International Society of Animal Professionals