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How Medical Conditions Impact Cat Behavior

Learn which medical conditions can contribute to abnormal cat behavior.

I always say cats are masters of disguise when it comes to hiding pain and other ailments, but even they may show behavioral changes because of illness. Just like sick humans can be depressed, withdrawn, or moody, so can cats. Obviously it’s impossible to cover everything, but we’ll look at the most common behaviors and connect them to possible medical conditions. My goal isn’t to scare you over possible diagnoses, especially since not all of these medical conditions are common. But I want to provide insight as to why the first step is usually diagnostics, even when your cat has a behavioral issue.

Fear or Anxiety

Fear is when a can is scared, and while this can turn to aggression if the cat is threatened, it doesn’t always. Sometimes fearful cats hide, while others may flatten their bodies to appear smaller.

Orange and white cat
Sunshine struggles with anxiety off and on because of a traumatic past.

Anxiety is when a cat is nervous or uneasy about an event or uncertainty. Remember that cats view things through a different lens than we do, because they are still hardwired to hunt and survive outdoors. Things that make sense to us can cause anxiety for them i.e. the sound of the vacuum cleaner.

Possible Medical Conditions That Cause Fear & Anxiety

  • Brain tumor
  • Dementia
  • Endocrine issues
    • Hyperthyroidism
    • Hyperadrenocorticism
    • Hypothyroidism
  • Epilepsy or seizures
  • Hormonal disorder
  • Toxins
  • Other diseases that affect the central nervous system

Aggression

Aggression is when a cat swats, nips, or bites, and sometimes even lunges, and it’s usually accompanied by hisses and growls. They can be aggressive toward people or other animals, and sometimes even objects. Hunting, playing, or even petting can make a cat so excited that they become aggressive. Cats can also get aggressive if their subtle body language warning cues are ignored.

Possible Medical Conditions That Cause Aggression

Tabby cat in bow tie
Gigi has abnormal front legs and walks on her ankles. We realized she was uncomfortable and she’s much less moody since starting pain management.
  • Brain tumors
  • Constipation
  • Dementia
  • Epilepsy or seizures (intermittent aggression)
  • Feline immunodeficiency virus (FIV)
  • Foreign body obstruction
  • Hearing or vision loss
  • Pain
    • Arthritis
    • Injury
      • Possible nerve damage or sensitive skin from a previously healed injury
    • Intervertebral disc disease (IDD)
    • Tooth or mouth issues
  • Other diseases that affect central nervous system
  • Response to trauma

Rage

orange cat on stratcher
We will never know exactly what caused Linux’s bouts of rage, but we can say there was something going on in his brain that he couldn’t control.

Rage is out of control aggression, that includes frenzied attacks with repeated kill bites (four fangs into the skin) on humans or animals. Typically, these cats can’t stop themselves and are responding to signals in their brain (aka it’s not personal). Although rage isn’t common, it does exist, and you can read about my experience with Linux and rage.

Possible Medical Conditions That Cause Rage

  • Brain tumors
  • Epilepsy or seizures

Housesoiling

black and white cat
Chuck Bass was marking when I first fostered him. I had a feeling it was territorial because it was on a vertical surface, but we ran a urinalysis just to be sure.

Housesoiling is when a cat empties their bladder or defecates outside of the litter box and on a horizontal surface. This is different from urine marking, which is when a cat sprays a small amount of pee on a vertical surface. Housesoiling is usually due to:

  1. Litter box aversion – Disliking something about the box itself.
  2. Substrate aversion – Disliking the litter.
  3. Location preference – Preferring another location over where the box is located.
  4. Surface preference – Preferring another surface to urinate or defecate on.

It’s crucial to rule out medical conditions for housesoiling first.

Possible Medical Conditions That Cause Housesoiling

  • Anal sac diseases
  • Bacterial, viral, or fungal infection (ex. FIV, panleukopenia, giardia, coccidia, etc.)
  • Colitis
  • Constipation
  • Dementia
  • Diabetes
  • Diarrhea
  • Endocrine issues
    • Hyperthyroidism
  • Extratesticular tumor (can happen in altered cats; the tumor appears in the same location)
  • Feline lower urinary tract disease (FLUTD)
    • Feline idiopathic cystitis
  • Foreign body obstruction (usually fecal housesoiling)
  • Hormonal disorder
  • Inflammatory bowel disease (IBD)
  • Kidney disease
  • Liver disease
  • Pain
    • Arthritis or joint pain – Difficulty getting into and out of the box
    • Strain or sprain – Could have injured themselves without you noticing
  • Urinary tract infection (UTI)

Disorientation & Confusion

Disorientation and confusion are common behavior traits you’ll see in aging cats, but they can occur from a variety of health issues as well.

Possible Medical Conditions That Cause Disorientation & Confusion

  • Dementia
  • Diabetes
  • Ear infections (feline vestibular disease)
  • Feline infectious peritonitis (FIP)
  • FIV
  • Hearing or vision loss
  • Liver disease
    • Cholangiohepatitis
    • Cirrhosis
  • Panleukopenia (aka feline distemper aka feline parvo)
  • Rabies
  • Seizures
  • Toxins

Increased Vocalization

Cats that are disoriented or confused may meow, howl, or yowl, but there are possible medical reasons for this as well. One of the best things you can do is video the behavior and show it to your vet. The main concern with this behavior is that your cat could be in pain, and you want to address that as soon as possible.

Possible Medical Conditions That Cause Increased Vocalization

  • Dementia
  • Depression – Often due to loss of family member (human or animal)
  • Endocrine issues
    • Hyperthyroidism
  • Hearing or vision loss
  • Heart disease
  • Hypertension
  • Separation anxiety
  • Toxins

Personality Changes, Moodiness & Irritability

An always sweet cat that’s suddenly swatty and grumpy, could have a medical condition. The same can be said for a cat that used to like having their ears scratched and now hisses if you try to do it.

Black and white cat
Lucy was under the weather and I could tell something was wrong. Her blood work was normal, so she was given fluids and anti-nausea meds. It was the right move … Turned out she was constipated and the fluids helped her #2.

Possible Medical Conditions That Cause Personality Changes, Moodiness & Irritability

  • Anemia
  • Any disease that affects the limbic system
  • Cardiac disease
  • Digestive issues
    • Nausea
    • Constipation
    • Diarrhea
  • FIP
  • Metabolic diseases
  • Rabies
  • Upper respiratory infection (URI)
  • Toxins
  • Toxoplasmosis

Different Activity Level

Black and white cat on bed
Alfredo suffers from chronic rhinitis, which is reoccurring upper respiratory issues (lots of sneezing and snot). Before a flare, he has a slight decrease in activity.

Typically, kittens’ activity level is off the charts, super seniors like to nap all day, and the kitties from young to old adulthood show behavior somewhere in the middle as they age. Excessive sleepiness or hyperactivity are red flags that something medical could be going on.

Possible Medical Conditions That Cause a Different Activity Level

  • Cancer
  • Diabetes
  • Endocrine issues
    • Hyperthyroidism
    • Hypothyroidism
    • Hypoadrenocorticism
  • Heart disease
  • Liver disease
    • Portosystemic shunt
    • Hepatic lipidosis
    • Cholangiohepatitis
  • Pain
    • Arthritis or joint pain
  • URI

Sleep Disturbances, Excessive Wandering, or Restlessness

We know cats are marathon nappers, but it’s important to keep an eye out for different sleep patterns that what your cat normally has. An older cat that isn’t sleeping a lot, wanders around constantly, or seems to have problems getting comfortable, could have a decrease in cognition, or it could be a health issue.

Possible Medical Conditions That Cause Sleep Disturbances, Excessive Wandering, or Restlessness

  • Brain tumor or trauma
  • Dementia
  • Endocrine issues
    • Hyperthyroidism
    • Hypothyroidism
  • FIV
  • Hearing or vision loss
  • Heart disease
  • Insomnia – usually due to environmental changes
  • Liver disease
  • Nervous system disorders
  • Pain
  • Toxins
  • Vitamin or mineral deficiency

Overgrooming or Undergrooming & Repetitive Chewing or Licking

In addition to catching your cat in the act, you can also tell your cat is obsessively grooming, chewing or licking if you find lesions or bald spots (alopecia).

Cats like to keep clean, but excessive grooming or undergrooming are indicators of a deeper issue. Keep in mind that very old cats and kittens tend to undergroom, just by natural of their ages. However, when the grooming is outside of the norm, there could be a medical reason.

Cat also chew on their fur and claws to clean themselves. They lick to self soothe injuries and painful areas and to clean wounds. While their saliva contains antibacterial, painkilling, and healing properties, it also has a lot of bad bacteria. If a cat chews or licks a minor scrape or scratch and leaves it alone, it will likely heal. But if they constantly lick more serious injuries or wounds, they are at high risk for an infection.

Black and white cat in kitchen
Pepe has liver disease and hyperthyroidism, but his only behavioral indicator is that he pulls out his fur during grooming. Blood work shows levels are off but he purrs and plays like a normal kitty.

Possible Medical Conditions That Cause Overgrooming, Undergrooming, and Repetitive Chewing or Licking

  • Allergies
    • Food
    • Environmental
    • Flea
  • Bacterial dermatitis
  • Endocrine issues
    • Hyperthyroidism
  • External parasites
    • Fleas
    • Mites
  • Feline lower urinary tract disease (FLUTD) (cat may lick urethra frequently causing inflammation)
  • FIV
  • Foreign body obstruction
  • Fungal dermatitis
    • Ringworm
  • Mineral deficiency
  • Obsessive compulsive disorder (OCD)
  • Pain
    • Arthritis
    • Bladder infection
    • Spin or disc issue
  • Pancreatitis
  • Stress
  • Toxins

Rule Out Medical Conditions First

As you can see, many medical conditions can contribute to your cat’s changing behavior. Vets like to run diagnostics to rule out medical conditions first because if there’s something medically wrong, you can do behavior modification all day with no impact.

Sources

Center, Sharon. Merck Manual, Veterinary Manual. Disorders of the Liver and Gallbladder in Cats.

G. Langsberg, G., Hunthausen, W., and Ackerman, L. Behavioral Problems of the Dog & Cat.

Horwitz, Debra. VCA. Cat Behavior Problems: House Soiling.

Maciorakowski, Lisa. MSCPA Angell. Overgrooming Cats.

Parker, Richard. Senior Cat Wellness. Do Cats Have Antiseptic Tongues?

PetMD Editorial. Anxiety and Compulsive Disorders in Cats.

Tauge, Angela. Hill’s Pet. What Causes Cat and Dog Insomnia?

By LizsKittyBootCamp

I foster cats and kittens, specializing in behavioral cases.

2 replies on “How Medical Conditions Impact Cat Behavior”

Thank you. And I only listed some of the more common ones. Crazy right?!

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