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Unpack the critical medical considerations in dog aggression cases with expert insight from Dr. Amber Batson (BVetMed MRCVS). As both a practicing vet and a leading behaviourist through her Understand Animals UK venture, Dr. Batson is uniquely qualified to explore how underlying health issues influence canine behaviour.
For several years, it has become increasingly common for veterinarians and dog caregivers to recognise that pain in the dog’s body can be a driving force or contributing factor in the dog exhibiting aggressive behaviours.
The most obvious pain we can recognise in our pets is when there is a problem affecting their limbs. Pain in muscles, joints, connective tissues, and bones may manifest as a change in the activities a dog can perform, in the way they move around, or, most obviously, a significant limp.
However, there are other sites of potential pain in our dogs’ bodies that can motivate self-defence actions. Examples include ear infections, dental disease, and gut pain, as some of the most common conditions I encounter in my caseload (working as a vet and a behaviourist in the UK).
Pain is not the only consideration
Pain caused by disease or injury is not the only medical “motivator” we should consider in a dog showing aggressive actions. There are several other disease processes, some of which are unlikely to cause any pain, that have been linked with aggressive behaviours in dogs.
Epilepsy
One such example is epilepsy. Epilepsy is most commonly “idiopathic” in the dog, meaning we don’t fully understand why it occurs, which is different from seizures that occur because of an infection, toxins or tumours.
Whilst many of us might think of epileptic seizures as being a dog that falls over, losing consciousness and paddling on the ground, epilepsy in dogs can also present as “partial” or “focal” seizures (this is where only one part or small region of the brain is affected by abnormal brain electricity, rather than the majority of the brain in a “generalised” seizure).
Symptoms of a “partial seizure” can be a limb twitching repetitively, salivation - sometimes accompanied by vomiting, or pacing, whining, staring or comfort seeking. [1]
Focal seizures are less commonly associated with a loss of consciousness. Depending on the exact brain area affected, they can impact motor movements, sensory experiences, the autonomic nervous system, or emotional centres, resulting in wildly varying behavioural expressions.
Dogs are more likely to bite during an epileptic seizure, whether unconscious and fitting in a generalised seizure, or whether conscious and feeling “weird” in a focal or partial seizure. This can be because abnormal electrical activity in the brain activates “aggression” pathways, resulting in involuntary aggressive acts, or because the dog is scared and driven to intense self-protection mechanisms.
However, it is not just during the seizure itself that aggression risks are increased in these individuals. Epilepsy has been linked to an increased tendency to anxiety or fear, as well as causing cognitive impairments, such as lower trainability.
These emotional and memory changes can significantly change the personality and behavioural traits of an individual once the disease process has started in their brain. Diagnosing and treating epilepsy may therefore be an essential part of working effectively with a dog who has shown aggressive behaviours.
Endocrine diseases
Changes in glands in the body, such as those that produce hormones, can also occur due to disease processes and may impact aggressive behaviours.
Thyroid gland
Considering the thyroid gland, both underactivity and overactivity have been associated with aggression.
Hypothyroidism (underproduction of thyroid hormones) has been linked to increased withdrawal/depressive states. It may perhaps play a role in anxiety/fear issues, as well as an increase in aggressive tendencies. There remains discussion in current veterinary research about how commonly behavioural signs are seen without other physical symptoms.
It is most likely that some physical signs would be present in the dog with this disease, as well as behavioural changes.
Common physical signs of an underactive thyroid include weight gain, symmetrical hair loss, changes in skin pigmentation, and lethargy. Some studies have not found a link between hypothyroidism and aggression, but consideration of this disease may remain relevant in some aggression cases. [2]
There has been an increase in the number of canine hyperthyroid cases (overproduction of thyroid hormones) in recent years (although overall, it remains a rare diagnosis in dogs). Several cases have been attributed to the consumption of uncooked thyroid gland as part of a raw-meat-based diet, although a minimal number of cases have now been linked to dried meat treats as well.
There has been an increase in the number of canine hyperthyroid cases (overproduction of thyroid hormones) in recent years (although overall, it remains a rare diagnosis in dogs). Several cases have been attributed to the consumption of uncooked thyroid gland as part of a raw-meat-based diet, although a minimal number of cases have now been linked to dried meat treats as well.
There has also been a possible increase in the occurrence or diagnosis of thyroid-producing tumours. An overactive thyroid gland can result in weight loss, increased urination and drinking, as well as behavioural signs of agitation, restlessness and possibly aggression. [3]
Adrenal gland
Diseases that affect adrenal gland function, such as Cushing’s disease, which is often used to describe an overactive adrenal gland, and Addison’s disease, which is used to describe an underactive adrenal gland, may also contribute to behavioural changes, including aggression.
The main behavioural change reported in dogs with adrenal gland overactivity is increased hunger and thirst, which may manifest as the development of scavenging, coprophagia or resource guarding (most frequently, food) behaviours.
Adrenal gland
Diseases that affect adrenal gland function, such as Cushing’s disease, which is often used to describe an overactive adrenal gland, and Addison’s disease, which is used to describe an underactive adrenal gland, may also contribute to behavioural changes, including aggression.
The main behavioural change reported in dogs with adrenal gland overactivity is increased hunger and thirst, which may manifest as the development of scavenging, coprophagia or resource guarding (most frequently, food) behaviours.
Additional behaviour change is not well reported in dogs at present. However, in people, an overactive adrenal gland has been linked with anxiety and fear disorders, irritability and depression, so this may need consideration in aggressive dog behaviours.
I look forward to expanding on this topic in at least two of my presentations at the 2025 APDT Australia Conference (2-5 October):
When a dog develops aggression as a behavioural sign, it is essential to look for the motivations that underlie the actions.Pain and non-painful diseases can be both the sole cause of the development of aggression or they can be contributing factors. Either way, a thorough assessment of health often plays a crucial role in addressing aggression in our pet dogs.
I look forward to expanding on this topic in at least two of my presentations at the 2025 APDT Australia Conference (2-5 October):
- Sick as a dog: how ill health influences behaviour
- A Pain in the ****: Why recognising and considering pain is essential in behaviour modification.
written by Dr. Amber Batson, reprinted (with permission) from APDT Click! Magazine | Issue 130 | August 2025
Receive Click! Magazine as a full Member of the Association of Pet Dog Trainers Australia (APDT). For details, visit https://apdt.360membership.com.au
About the author:
Amber Batson graduated from the Royal Veterinary College, London, in 1999 and has worked in clinical vet practice ever since.
About the author:
Right from the beginning of her vet career, she realised the intrinsic links between health/disease and dog behaviour and how many interactions with dogs require understanding dog communication and their physical and emotional needs.
Amber undertook several years of part-time behaviour education alongside her veterinary work and then, in 2007, set up her own business, Understand Animals, to bridge the gap between emerging behavioural science and its practical application to help people and their dogs have the best relationships.
Amber undertook several years of part-time behaviour education alongside her veterinary work and then, in 2007, set up her own business, Understand Animals, to bridge the gap between emerging behavioural science and its practical application to help people and their dogs have the best relationships.
References:
[1] Packer, RM and Volk, HA, (2015) Epilepsy beyond seizures: a review of the impact of epilepsy and its comorbidities on health-related quality of life in dogs. Veterinary Record, 177(12), 306–315. DOI 10.1136/vr.103360
[2] Hrovat, A, et al, (2019) Behavior in dogs with spontaneous hypothyroidism during treatment with levothyroxine. Journal of veterinary internal medicine, 33(1), 64–71. DOI 10.1111/jvim.15342
[3] Camps, T, et al, (2019) A review of medical conditions and behavioural problems in dogs and cats. Animals, 9(12), 1133. DOI 10.3390/ani9121133
Related Stories:
Dog Bites: the Subtle Warning Signs
Study into Canine Epilepsy Helps Owners Identify Triggers
Understanding and Handling Dog Aggression
[1] Packer, RM and Volk, HA, (2015) Epilepsy beyond seizures: a review of the impact of epilepsy and its comorbidities on health-related quality of life in dogs. Veterinary Record, 177(12), 306–315. DOI 10.1136/vr.103360
[2] Hrovat, A, et al, (2019) Behavior in dogs with spontaneous hypothyroidism during treatment with levothyroxine. Journal of veterinary internal medicine, 33(1), 64–71. DOI 10.1111/jvim.15342
[3] Camps, T, et al, (2019) A review of medical conditions and behavioural problems in dogs and cats. Animals, 9(12), 1133. DOI 10.3390/ani9121133
Related Stories:
Dog Bites: the Subtle Warning Signs
Study into Canine Epilepsy Helps Owners Identify Triggers
Understanding and Handling Dog Aggression
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