Health Problems That Can Masquerade As Bad Behaviour In Cats

At a glance

About: Several diseases can lead to changes which pet owners may put down to bad behaviour, this highlights the importance of a thorough medical evaluation for any cat displaying undesirable behaviour to determine if there is a medical cause.

What kind of behaviours can be caused by disease?

  • Going to the toilet outside the litter tray
  • Overgrooming which can lead to baldness
  • Sensitivity to touch
  • Aggression
  • Excessive crying


  • Neurological disturbances
  • Oral pain
  • Hyperthyroidism
  • Urinary tract diseases
  • Arthritis
  • Skin diseases
  • Liver disease
  • Pica
  • Cognitive dysfunction syndrome (senility)


Many diseases can manifest as behavioural changes and can be mistaken for bad behaviour, and can be a source of frustration for the pet owner and prolonged suffering for a cat whose condition may go undiagnosed. With an early diagnosis, it may be possible to treat or at least manage these conditions, which will see an improvement in symptoms.

Not all of these diseases will lead to behavioural changes, but all do have the potential to do so.

Neurological disease

Neurological diseases are disorders of the central and peripheral nervous system, which make up the brain, spinal cord, cranial nerves, peripheral nerves, nerve roots, autonomic nervous system, neuromuscular junction, and muscles.

Diseases that affect the neurological system include liver disease (see below), vascular disease, brain tumours (benign and malignant), infections, trauma and toxins.

Symptoms of neurological disease can be varied but include incoordination, confusion, head pressing, seizures, blindness and behavioural changes which include aggression.

Urinary tract disease

Urinary tract disease refers to several disorders of the cat’s urinary tract, which is consists of the upper and lower urinary tracts. Cystitis, bladder and kidney infections, urinary crystals or stones can lead to pain when urinating, or a sense of urgency.


  • Crying in the litter tray
  • Blood in the urine
  • Pain when touched
  • Inability to urinate
  • Frequent genital licking
  • Urinating outside the litter tray

Male cats are at increased risk of urinary blockages due to their narrow urethra; if the cat can’t urinate, toxins build up in the blood, which eventually leads to death.


A common endocrine disease caused by a benign hormone-secreting tumour of the thyroid gland. Hyperthyroidism is the most common endocrine disorder in cats and is seen most frequently in middle-aged to senior cats.


  • Weight loss
  • Increased appetite
  • Poor coat condition
  • Thickening of the claws
  • Jittery behaviour
  • Overgrooming
  • Restlessness
  • Increased vocalisation
  • Aggression

Oral pain

Broken teeth, gum disease, feline odontic resorptive lesions, dental abscess, oral cancer are all common oral diseases that can cause long or short term pain.


  • Drooling
  • Reluctance to eat
  • Bad breath
  • Bleeding from the mouth
  • Hiding
  • Reluctance to be touched around the head area
  • Aggression

Skin diseases

Cats are prone to developing skin diseases which can be due to external parasites (fleas and mites), allergies and immune-mediated disorders. One study found that 76% of cats with suspected psychogenic alopecia had an underlying skin disease.


  • Intense itching and scratching
  • Excessive grooming
  • Alopecia (hair loss)


A painful condition in which the shock-absorbing cartilage which cushions the joints wears down and is eventually lost. When osteoarthritis develops, this slippery layer breaks down and wears away exposing the bones, causing pain, inflammation, and stiffness. As the disease progresses, loss of movement can occur in the affected joint which can impact the cat’s mobility, who can no longer jump or climb as well as he or she used to be able to do.

Osteoarthritis is under-diagnosed, and by the time clinical signs appear, the cat is in significant pain. Studies have revealed the following:

  • 20% of cats over 1 have some signs of arthritis
  • 60% of cats over 6 have arthritis
  • 90% of cats over 12 have arthritis


  • Stiffness upon waking
  • Reluctance to move
  • Grooming less
  • Lameness
  • Swelling around the affected joint(s)
  • Aggression when touched
  • Going to the toilet outside the litter tray

Pica or wool sucking

Pica in cats is a potentially serious condition where they have an abnormal compulsion to eat non-food substances such as clothing, plastic, wool etc. The preferred food choice is generally reserved for the same object.

Objects can include clothing such as socks and blankets. Pica is an obsessive-compulsive disorder; however, several medical conditions can also lead to inappropriate chewing and eating non-food objects.

Cognitive dysfunction syndrome

Just like humans, cats can develop age-related cognitive changes as they move into their senior years. Cognitive dysfunction syndrome (senility) has been found in 30% of cats between 11 and 14 show signs of CDS, this figure jumps up to 50% in cats over 15 years of age and up to 80% in cats aged 16 and onwards.

The cause is not known, the formation of plaques in the brain, reduced blood flow due to damaged blood vessels and chronic free radical damage are implicated in the development of senility in people.


DISHAAL is an abbreviation that summarises the classic signs of CDS.

  1. Disorientation
  2. Interactions (changes in interactions with owners, other pets and the environment)
  3. Sleep-wake cycle disturbances
  4. Housesoiling
  5. Activity (changes in/repetitive)
  6. Anxiety
  7. Learning

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  • Julia Wilson, 'Cat World' Founder

    Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio

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