Health conditions that can lead to behavioural changes in your dog

Health conditions that can lead to behavioural changes in your dog

Health & Safety

Any form of illness, injury or chronic disorder can have wide-ranging implications for your dog’s general health and wellbeing, and as well as the obvious physical effects of such problems, illness can lead to behavioural changes as well. Some of these are self-evident, such as the fact that a dog that is in pain for any reason is likely to become defensive about being touched or handled, which can manifest as aggression, but a range of other conditions can lead to genuine behavioural changes on a chemical level, due to the ways in which they affect the brain and responses.

For some health conditions that present with few to no symptoms, such behavioural problems might be your first indication that something is wrong, and this is why it is always a good idea to get your dog examined by your vet if something changes, before you start looking at behaviour modification and assume that your dog’s acting out is purely a behavioural, and not a medical issue.

In this article, we will look at some of the canine health conditions that can cause behavioural changes in your dog, how to identify them, and what issues they can cause. Read on to learn more.

How do health conditions cause behavioural changes?

As mentioned, if a dog feels ill or has a painful area of the body, it is very natural that they will act accordingly, trying to protect the area that hurts or generally keep people away from them. This is simply an evolutionary response to pain and recovery.

Some conditions, on the other hand, can lead to tangible mental and chemical changes in your dog, which can manifest as unusual or out of character behaviours, such as OCD-type behaviour patterns, unprovoked aggression, or generally, odd and inappropriate behaviours.

These conditions are usually ones that have an effect either directly on the brain, or on the hormones of the dog, although there are some exceptions. We will look at some of the most common conditions that can cause behavioural changes in the dog below.

Rage syndrome

Rage syndrome in dogs is also sometimes known as “Cocker rage syndrome,” as it is most commonly seen in Cocker spaniels, and to a lesser extent, other spaniel breeds. This condition is covered in detail here in a prior article, and whilst thankfully rare, the condition involves acute onset unprovoked aggression in the dog, which unfortunately, cannot be cured and usually means that the affected dog will have to be put to sleep.

Brain tumours

Understandably, any anomaly in the brain itself, or any condition that affects the brain such as a physical tumour, can have a wide range of both physical and behavioural effects on the dog. The behavioural changes caused by brain tumours can be highly variable, depending on what parts of the brain they affect, and can include problems such as loss of memory, lack of coordination, unprovoked aggression, and other out of character behaviours.


Encephalitis is a condition that leads to inflammation of the brain, which once more, has a wide range of implications for the dog’s physical health and emotional behaviour, and may include hallucinations, seizures, aggression, and a whole range of other problems too. Generally, if the inflammation can be brought under control and the condition treated, your dog’s behaviour will return to normal soon afterwards.

Thyroid disorders

The thyroid gland, located in the neck of the dog, is responsible for regulating the metabolism, weight, digestive system, activity levels, and mood. Two conditions can affect the thyroid, being hypothyroidism, when not enough thyroid hormones are produced, or hyperthyroidism, in which the hormone production goes into overdrive. Hypothyroidism can lead to anxiety, lethargy, weight gain and depression in dogs, as well as potentially aggression, whilst hyperthyroidism can cause hyperactivity, obsessive behaviours, and weight loss.

Both conditions can be controlled with medications.

Brachycephalic hydrocephalus

Hydrocephalus is a condition that leads to fluid gathering in the ventricles of the brain and face, which is much more common in brachycephalic dogs than others, due to their shortened muzzles. This can lead to agitation, out of character behaviour, petit mal or grand mal fits and possibly aggression, and how successfully this can be treated can vary considerably from case to case, but one of the potential treatment options includes the use of corticosteroids to reduce the amount of fluid that the body produces.

Other issues

These are by no means the only health conditions that can lead to behavioural changes in the dog; perhaps the best-known condition of all that leads to potential aggression and other out of character behaviours of this type is rabies, although in the UK we are fortunate enough to not have to consider this issue, as rabies has been eradicated here.

Other potential diagnosis can include various seizure disorders such as epilepsy, and a wide range of other conditions that are systemic, affect the brain, or affect the body’s hormonal balance can all lead to issues too, which is why talking to your vet is vital in the first instance.



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