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Mythbusting The Term Rage Syndrome

Mythbusting Rage Syndrome: Looking at Science and Causes of Behaviour Changes rather than Labels.

'Rage Syndrome' as a term, is attributed to Dr. Roger A Mugford, and described as sudden and unprovoked aggressive behaviour in dogs, which was first discussed in the 1970’s and 80's. The word rage comes from the Latin word rabies-rabere (to rage). Though this condition has no link to the disease rabies, I think we need to be aware of language and its negative effect, which I will discuss.

Scientific and veterinary specialists debated this disorder through lack of scientific evidence, and suggested there was instead behavioural and medical conditions that were the result of such changes.

Instead we refer to these behaviours and symptoms as, 'Idiopathic Aggression'. The definition of idiopathic is: “relating to or denoting any disease or condition which arises spontaneously or for which the cause is unknown.” It can be seen as a neurological disorder clinically, and is then investigated.

The term rage syndrome was originally used to describe a set of behaviours that were occurring in a disproportionate number of cocker Spaniels. Hence, sadly linked to this particular breed. However, the same aggressive behaviours and symptoms were also discovered in many other breeds, disproving this was breed specific. In a study from 2013, slightly lower levels of serum serotonin were found in English cocker spaniels that showed aggressive behaviours, than other dogs of other breeds. But importantly these variances were not significantly different between cocker spaniels and other breeds within the study.

Genetics and genetic factors may be a cause of these behavioural changes. Neurological abnormalities that some studies link to abnormalities in the amygdala and hypothalamus that regulate responses. Hormonal imbalances, such as serotonin impact behaviour. Serotonin values observed in aggressive dogs were lower than in non-aggressive dogs (Bochis et al, 2022). There are many studies that show that low levels of serotonin are associated with aggressive behaviour in many species. Environmental context is also important, along with learning history that can exacerbate behaviour. Increasing serotonin can be discussed with a veterinary professional, from diet, supplements and nutrition support via tryptophan rich food and medication.

Aggression in dogs is often a reason for abandonment and/or euthanasia. Studies from recent years related to negative dog behaviour, especially aggression in dogs, and in particular its causes, have not been fully understood to this day. Recent studies show that factors such as disease, hormone balance, and diet may be associated with adverse aggressive behaviour in dogs. However, new research also suggests that it is possible to correct or avoid the occurrence of undesirable aggressive behaviour in dogs by correctly reading dogs’ body language, understanding their basic needs, adjusting their diet to training, identifying disease early, introducing proper socialisation, and understanding that aggression is a natural part of canine communication.

Unfortunately, an article that was published in 2023, in regard to disorders picked up in English Cocker spaniels has again brought this into focus. The results were stated to aid veterinary surgeons in giving evidence-based breed-adapted health information to dog owners and support breeding organisations. However, due to this newly published article the term rage syndrome has been picked up again in relation to English cocker spaniels sadly.

My conclusion is that we avoid using the term 'Rage Syndrome', as aggressive behaviour is linked to more complex clinical diagnosis, requiring investigation when behaviour changes present. Instead of placing a label we need to look at a dog as a whole, from genetics, epigenetics, hormonal imbalances, neurological abnormalities, learning history, socialisation, individual needs being met, and more. Always refer a client to a veterinary professional, who can also refer to a clinical or qualified behaviourist.

This article has some great insights and information written by vet and gundog specialist Vicky Payne, where she says; "Most dogs labelled this way do not have any such thing; instead they are frustrated working-bred dogs who have not been given an outlet for their hunting and retrieving."


Marta Amat, Susana Le Brech, Tomàs Camps, Carlos Torrente, Valentina M. Mariotti, José L. Ruiz, Xavier Manteca, Differences in serotonin serum concentration between aggressive English cocker spaniels and aggressive dogs of other breeds, Journal of Veterinary Behavior, Volume 8, Issue 1, 2013, Pages 19-25, ISSN 1558-7878,

Engdahl, K.S., Brodbelt, D.C., Cameron, C. et al. Demography and disorders of English Cocker Spaniels under primary veterinary care in the UK. Canine Med Genet 10, 4 (2023).

Kleszcz, A.; Cholewińska, P.; Front, G.; Pacoń, J.; Bodkowski, R.; Janczak, M.; Dorobisz, T. Review on Selected Aggression Causes and the Role of Neurocognitive Science in the Diagnosis. Animals 2022, 12, 281.

Overall K.L. Clinical Behavioral Medicine for Small Animals. 1st ed. Mosby; Mosby, MO, USA: 1997. pp. 88–137.


Serotonin - is a chemical neurotransmitter that carries messages between nerve cells in the brain and throughout your body. Serotonin plays a key role in such body functions as mood, sleep, digestion, optimism and more.

L-Tryptophan – is a natural amino acid found in many proteins which is involved in the production of the hormone Serotonin.


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