By Norma Jeanne Laurette ​

​Many people view canine aggression as an exclusively behavioural issue. Although there are numerous contributing factors that cause or worsen behavioural aggression, there are also reasons many are not aware of such as medications and health issues. If health problems or prescription drugs are the cause or are exacerbating the problem, behaviour modification will not be successful without addressing these factors as well. Because of this, any responsible canine behaviour therapist will always investigate these possibilities before treating aggression as purely behavioural.

Imbalances in brain chemistry, endocrine disorders, pain and neurological abnormalities can cause aggression. One of the main physiological contributors is an imbalance in neurotransmitters, particularly serotonin. As with humans, low levels of serotonin has been linked to increased impulsivity and aggression in dogs R1. Abnormalities in dopamine and norepinephrine can also contribute to heightened arousal, reactivity and aggression.

Endocrine issues, such as hypothyroidism have also been to blame. Low thyroid hormone levels can cause irritability, mood swings and sudden outbursts R2. Thyroid function can be evaluated through blood work and if necessary, medical intervention can help restore hormone levels to normal.

Pain is another factor. Conditions such as arthritis, dental disease or injuries can make dogs more reactive and less tolerant of other dogs or being handled R3. Neurological conditions such as brain tumours or epilepsy can also contribute to increased irritability or aggression, which occurs when pressure affects specific brain regions or when seizure-related changes alter brain chemistry R4.

Medications and underlying health conditions can play a significant role in influencing aggression. Anything that contributes to fatigue, discomfort, confusion or pain can lower an individual’s threshold for irritability and lead to outbursts of aggression R25. Chronic pain, neurological disorders and side effects from certain medications can disrupt normal brain chemistry and as a result, the dog’s ability to control its emotions R26. Conditions that cause persistent fatigue or cognitive impairment such as sleep disorders or metabolic imbalances can also add to frustration and reduce tolerance to stress, increasing the likelihood of aggressive behaviour R27.
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It’s important to be aware that some medications prescribed to dogs for various health and behaviour issues can also contribute to or exacerbate aggressive behaviour. Drugs that affect brain chemistry including corticosteroids, some anticonvulsants and pain medications can increase irritability or impulsivity in dogs R5. Untreated or poorly managed medical conditions such as hypothyroidism, chronic pain or neurological disorders can also cause aggression or make it worse. Guardians should be aware of all potential side effects, risks and prognosis associated with medications and treatments in order to make informed decisions in the best interest of their dogs.

Corticosteroids R6 R50
Used to treat inflammation and autoimmune conditions.

• Prednisolone
• Methylprednisolone

Anticonvulsants R7 R8
Used to control seizures.

• Phenobarbital
• Levetiracetam (Keppra) R47
• Zonisamide
• Gabapentin

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) R9 R48
Used to treat inflammation and pain.

• Carprofen
• Meloxicam

Selective Serotonin Reuptake Inhibitors (SSRIs) R15
Used to treat behavioural issues.

• Fluoxetine (Prozac) R31 R52
• Sertraline (Zoloft) R32
• Paroxetine (Paxil) R33
• Fluvoxamine (Luvox) R34

Tricyclic Antidepressants (TCAs) R10
Used to treat behavioural issues.

• Clomipramine (Clomicalm) R49

Benzodiazepines (Anti-Anxiety/Sedatives) R11
Used to treat anxiety and seizures.

• Diazepam (Valium – Seizures)
• Alprazolam (Xanax – Anxiety)

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Atypical Antipsychotics/Sedatives R12
Used to calm anxious dogs.

• Acepromazine R51

Arthritis/Joint Disease R35
Chronic pain from inflammation of the joints can cause irritability and aggression.

Blindness/Vision Impairment R42
Losing sight can cause a dog to feel vulnerable, which can result in fear, defensive behaviour and aggression.

Brain Tumors R37
Brain tumors can lead to seizures and behavioural changes including aggression.

Canine Distemper R47
The canine distemper virus attacks the respiratory, gastrointestinal and nervous systems. It can cause encephalitis, which is painful and seizures, which can result in confusion, irritability and aggression.

Cognitive Dysfunction Syndrome (CDS) R41
Cognitive decline associated with aging can cause confusion, disorientation, fear, anxiety, sleep disturbance, reduced impulse control, frustration and memory loss, which can all contribute to aggressive behaviour.

Deafness/Hearing Loss R43
When a dog’s hearing declines, it can be easily startled resulting in fear, defensive behaviour and aggression.

Dental Disease R36
Dental disease can cause pain resulting in irritability and aggression.

Encephalitis R14
Encephalitis causes inflammation on the brain. It is painful and can cause seizures, cognitive and behavioural changes including aggression.

Hypothyroidism (Underactive Thyroid) R10
Hypothyroidism slows down brain activity, which can result in physical pain or discomfort, fatigue, depression, anxiety, irritability and a low tolerance for frustration. It can affect cognition, emotional instability and responsiveness, and lead to fear, defensive behaviour, reactivity and aggression.

Hyperthyroidism (Overactive Thyroid) R11
Hyperthyroidism speeds up brain activity, which can result in physical pain or discomfort, weight loss, muscle tremors, rapid heart beat, sleep disturbances, cognitive changes, fear, defensive behaviour and aggression.

Hydrocephalus R12 R40
Hydrocephalus is a buildup of excess cerebrospinal fluid that leaks inside the skull causing the brain to swell. It can lead to vision impairment, gait abnormalities, seizures and pain, as well as behavioral changes including aggression.

Hypoglycemia R14
The brain relies mainly on glucose for energy and when blood sugar falls too low, the brain doesn’t function properly. This can cause weakness, confusion, anxiety, restlessness, irritability, panic, disorientation, neurological impairment, tremors, seizures and sudden changes in mood and behaviour including aggression.

Kidney Disease R45
When toxins accumulate in the kidneys it can cause kidney failure. It can also affect the brain and nervous system as well as interfere with muscle function and nerve signalling. This can result in fatigue, headaches, sensitivity, nausea, digestive upset, high blood pressure, cognitive dysfunction, confusion, disorientation, irritability, a lower tolerance for other animals, sounds and handling. It can result in fear, defensive behaviour and aggression.

Liver Disease R44
Toxic buildup due to liver dysfunction can cause encephalopathy, low blood sugar and nutrient imbalances, which can result in confusion, disorientation, anxiety, personality changes, irritability, seizures, abdominal pain, nausea and compromised impulse control. Not only can this cause defensive and aggressive behaviour, the medications used to treat liver disease can increase aggression.

Meningitis R39
Meningitis is an infection that causes inflammation of the fluid and membranes surrounding the spinal cord and brain. It’s painful and can result in irritability and aggression.

Seizure Disorders R38
During a seizure, abnormal electrical activity in the brain can trigger sudden, involuntary behaviours such as growling, snapping or attacking. Changes in brain chemistry caused by seizures can lead to personality changes between episodes, including reduced tolerance and increased aggression. Following a seizure, a dog can be temporarily blind, disoriented, confused and anxious, which can result in defensive aggression if they are touched or handled. When seizures are linked to inflammation, tumours or trauma, impulse control can be compromised. To make matters worse, the anticonvulsants prescribed for seizures can also cause or exacerbate aggression.

Tick-Borne Diseases R46
Infections transmitted by ticks can cause fever, neurotransmitter and hormone imbalance, liver and kidney damage, encephalitis or meningitis, joint and muscle stiffness, all of which can be painful and lead to irritability and aggressive behaviour.

Rage Syndrome R13
Rage Syndrome is a rare seizure-related condition often misdiagnosed as idiopathic aggression. It presents as sudden, explosive aggression and is often managed with anticonvulsants. Although “rage syndrome” and “idiopathic aggression” were once believed to be the same thing, they are not. 

Rage syndrome is neurological and caused by a seizure disorder that affects the regions of the brain that control behaviour and aggression. During an episode, the dog often exhibits a glassy-eyed stare or trance-like state before the attack and afterward may quickly return to normal or appear confused. In either case, the dog is entirely oblivious to what just occurred. For this reason, aggression caused by rage syndrome is considered a neurological issue rather than a behavioural one R29.

Idiopathic Aggression
Idiopathic aggression is not the same as rage syndrome. According to Oxford Dictionary, idiopathic means “relating to or denoting any disease or condition which arises spontaneously or for which the cause is unknown”. What this means is that idiopathic aggression is sudden, severe, unpredictable aggression where no medical, neurological or behavioural trigger can be identified.

The idiopathic diagnosis is given after veterinarians and behaviour experts rule out potential causes. A veterinarian looks for neurological issues, thyroid disease and pain, while a behaviour expert looks for behavioural causes. All “idiopathic” means is that through the process of elimination, the veterinarians and behaviour experts working with the dog have not pinpointed the cause R28.
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It doesn’t mean that there isn’t a legitimate cause because there always is, even if we can’t find it and there’s always the possibility of an unidentified trigger. Likewise, there could be an undetected health issue.

​The canine blood brain barrier (BBB) is a group of cells that controls the exchange of substances between the bloodstream and the brain, helping to maintain balance in the central nervous system. Although designed to block harmful molecules, the BBB is not completely secure. Stress hormones, inflammatory molecules, environmental toxins as well as some medications and infectious organisms can cross or disrupt it R53.

When this happens, the brain’s delicate chemical balance can be disturbed, affecting neurotransmitters such as serotonin and dopamine, which are essential for controlling mood and behaviour R54. A weakened or overexposed BBB can contribute to increased reactivity or aggression when compounds that should not cross the brain barrier interfere with emotional regulation and impulse control R55.

Supporting a healthy BBB requires a combination of diet and lifestyle. Antioxidant-rich foods such as blueberries, spinach and omega-3 fatty acids can help reduce oxidative stress, which is a key factor in the BBB breaking down R56. Healthy levels of vitamins E and C also play an important role in maintaining the strength of the barrier R57. Balanced nutrition, maintaining a healthy weight and avoiding highly processed foods help reduce chronic, widespread inflammation and support overall brain health R58. Regular exercise, stress management and control of chronic conditions such as diabetes or hypertension are also important for preserving a healthy functioning BBB R59. Combining these strategies will help reduce the impact of harmful chemicals on behaviour and can help lower the risk of aggression caused by neurological imbalance.

​Although holistic options are generally considered safer than pharmaceuticals, they are not entirely without risk. Inappropriate dosing of herbal supplements or the use of unsafe essential oils can cause toxicity. A lack of regulation in over-the-counter products can lead to varying results or contamination. Although generally accepted as a safe treatment, acupuncture requires skill to be used effectively and avoid injuring the dog. 

Holistic interventions should never be the sole solution but instead, only one part of a multi-faceted treatment plan. Aggression in dogs can have behavioural, physiological and/or pharmaceutical causes or contributors that all need to be identified and addressed. While some prescription medications may help, they all come with risks that must be weighed against the benefits. The best approach is one that considers these three strategies: eliminating physiological and pharmaceutical contributors, safe holistic options as well as using behaviour modification techniques to resolve the underlying emotional issues. Using prescription drugs is a personal choice that I avoid whenever possible.

​Aggressive dogs are not happy dogs, and trying to stop aggressive behaviour or any behaviour for that matter with punishment only causes the fear, stress and anxiety that are at the very root of aggression. When aggression is caused by illness or pharmaceuticals, punishment is not only cruel – it’s pointless, on par with “beating a dead horse.” Every aggressive dog needs and deserves our compassion, patience and understanding and with our guidance can overcome their challenges to ensure emotional wellbeing and quality of life.

​R1: Olivier, B., & Mos, J. (1992). Serotonin and aggression. Annals of the New York Academy of Sciences, 652(1), 252–265. https://doi.org/10.1111/j.1749-6632.1992.tb34358.x
R2: Dodman, N. H., Mertens, P. A., Aronson, L. P., & Brown, D. C. (1996). Relationship between thyroid function and behavior problems in dogs. Journal of the American Veterinary Medical Association, 208(3), 353–356.
R3: Mills, D. S., Karagiannis, C. I., & Zulch, H. (2014). Stress—Its effects on health and behavior: A guide for practitioners. Veterinary Clinics of North America: Small Animal Practice, 44(3), 525–541. https://doi.org/10.1016/j.cvsm.2014.01.005
R4: Landsberg, G., Hunthausen, W., & Ackerman, L. (2012). Behavior problems of the dog and cat (3rd ed.). Saunders Elsevier.
R5: Overall, K. L. (2013). Manual of clinical behavioral medicine for dogs and cats. Elsevier.
R6: Freak on a Leash Dog Training article by Dr. Kate Mornement, CAAB — published October 18, 2024. (freakonaleashdogtraining.com)
R7: WebMD article “What to Know About Phenobarbital for Dogs” — published 2023. (webmd.com)
R8: Podell, M., Fenner, W. R., & Powers, J. D. (1995). Seizure control and side effects of phenobarbital and potassium bromide in dogs. Journal of the American Veterinary Medical Association, 207(5), 559–564.
R9: Budke, C. M., & Slater, M. R. (2009). Antiepileptic drug therapy in dogs. Compendium: Continuing Education for Veterinarians, 31(2), E1–E9.
R10: Panciera, D. L. (1994). Hypothyroidism in dogs: 66 cases (1987–1992). Journal of the American Veterinary Medical Association, 204(5), 761–767.
R11: Daminet, S., & Ferguson, D. C. (2003). Influence of drugs on thyroid function in dogs. Journal of Veterinary Internal Medicine, 17(4), 463–472. https://doi.org/10.1111/j.1939-1676.2003.tb02468.x
R12: Dewey, C. W., & da Costa, R. C. (2016). Practical guide to canine and feline neurology (3rd ed.). Wiley-Blackwell.
R13: Beaver, B. V. (2009). Canine behavior: Insights and answers (2nd ed.). Saunders Elsevier.
R14: Vaziri Law Group. (2023). Major factors that cause canine aggression. Retrieved from https://www.vazirilaw.com/major-factors-that-cause-canine-aggression
R15: Simpson, B. S., Landsberg, G., Reisner, I., Ciribassi, J., Horwitz, D., Houpt, K., … & McElroy, M. (2007). Effects of fluoxetine in canine separation anxiety. Journal of Veterinary Behavior, 2(4), 193–197. https://doi.org/10.1016/j.jveb.2007.09.002
R16: Crowell-Davis, S. L., & Murray, T. (2006). Veterinary psychopharmacology. Wiley-Blackwell.
R17: Mertens, P. A., & Unshelm, J. (1996). Aggressive behavior in dogs: A review. Journal of Veterinary Behavior, 1(1), 17–28. https://doi.org/10.1016/j.jveb.2005.06.002
R18: McGreevy, P. D., & Masters, A. M. (2008). Risk factors for separation-related distress and phobias in dogs: A pilot study. Journal of Veterinary Behavior, 3(4), 166–173. https://doi.org/10.1016/j.jveb.2008.04.003
R19: DeNapoli, J. S., Dodman, N. H., Shuster, L., Rand, W. M., & Gross, K. L. (2000). Effect of dietary protein content and tryptophan supplementation on dominance aggression, territorial aggression, and hyperactivity in dogs. Journal of the American Veterinary Medical Association, 217(4), 504–508.
R20: Re, S., Zanoletti, M., & Emanuele, E. (2008). Aggressive dogs are characterized by low omega-3 polyunsaturated fatty acid levels. Journal of Veterinary Behavior, 3(3), 111–116. https://doi.org/10.1016/j.jveb.2008.04.002
R21: Wynn, S. G., & Fougere, B. (2007). Veterinary herbal medicine. Mosby Elsevier.
R22: Xie, H., & Preast, V. (2010). Traditional Chinese Veterinary Medicine: Fundamental principles. Chi Institute Press.
R23: Sheppard, G., & Mills, D. S. (2003). Evaluation of dog-appeasing pheromone as a potential treatment for dogs fearful of fireworks. Veterinary Record, 152(14), 432–436.
R24: Kogan, L. R., Hellyer, P. W., Downing, R., & Schoenfeld-Tacher, R. (2019). Cannabis in veterinary medicine: A survey of the attitudes, experiences, and knowledge of veterinarians in North America. Frontiers in Veterinary Science, 5, 338. https://doi.org/10.3389/fvets.2018.00338
R25: Krakowski, M. (2003). Violence and serotonin: Influence of impulse control, affect regulation, and social functioning. Journal of Neuropsychiatry and Clinical Neurosciences, 15(3), 294–305. Discusses how physical and emotional stressors, including fatigue and pain, can lower impulse control and contribute to aggression.
R26: Kim, J. S., & Diamond, M. P. (2002). Medical conditions associated with aggression. Obstetrics and Gynecology Clinics of North America, 29(1), 1–14. Explores how various medical disorders and medication side effects may alter brain chemistry and increase irritability or aggression.
R27: Kamphuis, J., Meerlo, P., Koolhaas, J. M., & Lancel, M. (2012). Poor sleep as a potential causal factor in aggression and violence. Sleep Medicine, 13(4), 327–334. Examines the role of fatigue and sleep disruption in reducing tolerance to stress and promoting aggressive behaviour.
R28: Whole Dog Journal article by Dr. Kate Mornement, CAAB — published October 18, 2024.
R29: Teller, Dr. Lori. “Is Your Dog Aggressive? A Texas A&M Vet Explains ‘Rage Syndrome’.” Texas A&M University News, 2 April 2024, stories.tamu.edu/news/2024/04/02/is-your-dog-aggressive-a-texas-am-vet-explains-rage-syndrome/.Texas A&M Stories
R30: Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (2020). Assisting Decision-Making on Age of Neutering for 35 Breeds of Dogs: Associated Joint Disorders, Cancers, and Urinary Incontinence. Frontiers in Veterinary Science, 7, Article 388.
Bosch, G., Beerda, B., Hendriks, W. H., van der Poel, A. F. B., & Verstegen, M. W. A. (2007). Impact of nutrition on canine behaviour: current status and possible mechanisms. Nutrition Research Reviews, 20(2), 180–194. https://doi.org/10.1017/S095442240781331X
R31: Reference: Odore, R., et al. (2020). Behavioral Therapy and Fluoxetine Treatment in Dogs with Aggression. Frontiers in Veterinary Science. https://doi.org/10.3389/fvets.2020.00001PubMed Central
R32: Reference: PetMD. (2023). Sertraline (Zoloft®) for Dogs. https://www.petmd.com/pet-medication/sertraline-zoloft-dogsPetMD+2Veterinary Partner+2
R33: Reference: VCA Animal Hospitals. (2023). Paroxetine. https://vcahospitals.com/know-your-pet/paroxetineVca+1
R34: Reference: Bazin, I. (2022). Retrospective Study on the Use of Fluvoxamine in 72 Dogs with Anxiety Disorders. Journal of Veterinary Behavior. https://doi.org/10.1016/j.jveb.2022.01.001YMAWS+2ResearchGate+2
R35: Freak on a Leash Dog Training article by Dr. Kate Mornement, CAAB — published October 18, 2024.
R36: Pet Health Network article by Dr. Jennifer Coates, DVM — published January 13, 2015. Pet Health Network
R37: Veterinary Partner article by Dr. Lisa Freeman, DVM, PhD, DACVN — published February 27, 2025. Veterinary Partner
R38: Canine Estates article by Dr. Amber Batson, BVetMed MRCVS — published December 7, 2022. Australian Dog Lover
R39: Royal Canin Academy article — published October 2024. Wag!+6Vca+6Royal Canin Academy+6
R40: Vision for Animals article by Dr. Amber Batson, BVetMed MRCVS — published March 26, 2024. Vision for Animals Foundation
R41: Merck Veterinary Manual article by Dr. Jennifer Coates, DVM — published August 2024.
R42: PetMD article by Dr. Jennifer Coates, DVM — published September 2024.
R43: PetMD article by Dr. Jennifer Coates, DVM — published October 2024.
R44: PetMD article by Dr. Jennifer Coates, DVM — published November 2024.
R45: PetMD article by Dr. Jennifer Coates, DVM — published December 2024.
R46: PetMD article by Dr. Jennifer Coates, DVM — published January 2025.
R47: Veterinary Partner article “Levetiracetam for Dogs” by Dr. Lisa Freeman, DVM, PhD, DACVN — published February 27, 2025. (veterinarypartner.vin.com)
R48: VCA Animal Hospitals article “NSAIDs in Dogs” — published 2024. (vcahospitals.com)
R49: The Spruce Pets article “Clomipramine for Dogs” — published 2023. (thesprucepets.com)
R50: The Honest Kitchen article “Effects of Steroids on Dog Behavior” — published 2024. (thehonestkitchen.com)
R51: VCA Animal Hospitals article “Acepromazine for Dogs” — published 2024. (vcahospitals.com)
R52: PetMD article “Fluoxetine (Prozac) for Dogs” — published 2023. (petmd.com)
R53: Abbott, N. J., Patabendige, A. A., Dolman, D. E., Yusof, S. R., & Begley, D. J. (2010). Structure and function of the blood–brain barrier. Neurobiology of Disease, 37(1), 13–25. Overview of how the BBB functions and its permeability.
R54: de la Torre, J. C. (2012). Physiopathology of the blood–brain barrier: A review. Journal of Clinical Neuroscience, 19(1), 1–10. Discusses how neurotransmitter systems are affected by BBB disruption.
R55: Bortolato, M., & Shih, J. C. (2011). Behavioral outcomes of monoamine dysfunction: Aggression and beyond. Journal of Neurochemistry, 116(5), 974–986. Links neurotransmitter dysregulation to aggression.
R56: Joseph, J. A., Shukitt-Hale, B., Denisova, N. A., Prior, R. L., Cao, G., Martin, A., Taglialatela, G., & Bickford, P. C. (1998). Long-term dietary strawberry, spinach, or vitamin E supplementation retards the onset of age-related neuronal signal-transduction and cognitive behavioral deficits. Journal of Neuroscience, 18(19), 8047–8055. Shows antioxidant-rich foods protecting brain health.
R57: Cisternas, P., Silva-Alvarez, C., & Inestrosa, N. C. (2014). Vitamin E and neurodegeneration: Preventive and therapeutic opportunities. Frontiers in Neuroscience, 8, 46. Reviews role of vitamin E in protecting brain function.
R58: Calder, P. C. (2015). Marine omega-3 fatty acids and inflammatory processes: Effects, mechanisms and clinical relevance. Biochimica et Biophysica Acta (BBA) – Molecular and Cell Biology of Lipids, 1851(4), 469–484. Explains how omega-3s reduce inflammation, supporting BBB health.
R59: Zlokovic, B. V. (2008). The blood–brain barrier in health and chronic neurodegenerative disorders. Neuron, 57(2), 178–201. Highlights how lifestyle and systemic conditions affect BBB function.
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Photo by Nick Bolton on Unsplash

By Norma Jeanne Laurette ​

​The eyes can speak volumes about a dog’s emotional state. The eyes of a relaxed and happy dog will be round and hold a soft gaze. An aroused, frightened, stressed or anxious dog’s eyes will be wide with a hard stare and may show white around the eyes, known as whale-eye R8.

You’ll notice a dog’s eyes soften when interacting with people, other dogs and animals it likes and trusts. Looking away paired with slow blinks is often used to avoid conflict and ease tension R9, while the hard stare is reserved for moments before a sudden and impulsive reaction such as deterrent behaviour, lunging or biting. To learn about deterrent behaviour see our first book Blueprint To A Happy Dog R31.
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These communications are valuable when interacting with dogs because they help determine whether we should proceed, pause, turn away, blink, avoid eye contact, crouch, disengage or increase distance. Proactively supporting our dogs’ emotional wellbeing and behaviour by responding appropriately to their cues is essential to preventing stress and conflict R10.

​The movement of a dog’s ears provides subtle clues that reflect both emotion and focus. When a dog is alert, its ears will point forward and if it’s concentrating on something, they will turn toward the source of the sound. Ears flattened against a dog’s head indicate fear, while flickering ears suggest the dog is startled or investigating new sounds R11. Repeated ear twitching can signal that the dog is annoyed or mildly stressed. Ear twitching can be triggered by various factors, including changes in a handler’s tone, distractions or difficulty focusing – and can be caused by training sessions that progress longer than the dog’s ability to focus R12.
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Recognizing what a dog’s ears are communicating helps us adjust our interactions and training sessions to keep the dog relaxed and focused R13.

​As with humans, how a dog is feeling can be easily gauged by the tension in its lips. Dogs often use involuntary tightening of the lips and lip licking during social interactions as displacement behaviours when deciding whether to approach or retreat. It can indicate appeasement, mild stress or confusion R14. This often occurs when a dog is uncertain in new situations or environments or when meeting new animals or people. If it happens during a training session it can suggest that the dog has become overwhelmed and needs a shift in technique or a break R15.

​It’s important to use this information to make responsible choices that reduce the dog’s stress and prevent escalation R16.

​Not only is a dog’s sensory perception enhanced by its whiskers, it can also communicate its emotional state. When a dog is relaxed, its whiskers will rest against its muzzle. When stressed or aroused, they move forward, flare to the sides and become tense, which activates their sensory abilities R17. A dog’s whiskers are attached to sensitive nerve endings and blood vessels. When extended, a dog can feel subtle shifts in air currents enabling it to sense objects, other animals, navigate spaces and track prey R27.

However, whiskers can also communicate slight changes in mood R27. When a dog becomes reactive, just before barking, lunging or biting – the whiskers may flare forward as the eyes narrow and harden and the body stiffens R18.

Likewise, as the dog relaxes, the whiskers will once again rest against its face.
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Whiskers are one more piece of the puzzle to read when gauging a dog’s emotional state, in order to predict and prevent stress and unwanted behaviours R19.

​A micro-freeze occurs when a dog suddenly stops and holds its position for a brief moment. The freeze indicates a shift from either a relaxed state to alert or alert to calm R5. When this happens the dog is in conflict and making a choice about whether to continue engaging, stop, retreat or lunge and is an early warning that the dog is becoming stressed and could escalate to aggression.

We’ve seen this many times when dogs greet new dogs on leash. One or both will freeze, followed by play, disengaging or lunging. Because the freeze looks the same no matter the outcome, it can be difficult to predict the behaviour that will follow and know how to respond. This is one reason we avoid most leash greetings, the other being the unpredictability of the human at the other end of the leash. It’s important to put everything we know about the environment, the dog, as well as what its body is communicating into context to understand how it is truly feeling R6.
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This is key to helping handlers identify and avoid triggers that could lead to stress, anxiety, fear and aggression before it occurs R7.

​I can’t tell you how many times clients have told me their dog bit without warning. What many fail to realize is that there are almost always warnings, even though they don’t recognize them R20. When a dog communicates with subtle signals that it’s uncomfortable with a situation, it’s usually doing so with the intent to disarm the conflict.

However, there are also dogs that have been punished for showing teeth or growling, forcing them to suppress early warning communications and go straight to more intense behaviours such as lunging or biting R28. However, even though it looks as though the dog gave no warning, there’s often at least one brief micro-expression that precedes the behaviour. This is one reason why punishing a dog for expressing its emotional state is counter-productive. Since almost all aggression is caused by fear, these behaviours usually indicate a distressed dog attempting to cope with a perceived threat. Punishing a fearful dog only increases fear, stress and anxiety, which are the root cause of most aggressive behaviour R32 R29.

By treating the cause of the problem instead of punishing the symptoms we help the dog feel safer and more comfortable. When the dog is no longer stressed, the resulting behaviours will naturally fade. Just as with physical health, emotional health should also be addressed by treating the cause of the problem, not just the symptoms R30. The only time symptoms of aggression should be treated is when taking safety precautions to prevent bites.

For example, consider a child that’s allowed to torment or manhandle a dog. The dog may communicate its discomfort through subtle signals such as freezing, turning away, yawning, licking its lips, tightening its mouth or showing whale-eye, which is its way of saying, “I don’t like this.” If these warnings are ignored, the dog may be forced to escalate to deterrent behaviours R31, growling, snapping or biting R21. These incidents are always preventable and never the dog’s fault.

When we become fluent at reading micro-expressions, we will be able to spot stressors early and step in before they escalate to aggression, thus protecting the dog’s temperament, emotional wellbeing and potentially even its life R22. When dogs know their signals are understood, they become calmer, happier and more trusting, resulting in a deeper the bond of mutual trust and respect.

​Like any skill, reading micro-expressions can be learned and the more you practice, the better you become.

​To become a micro-expression expert one must first understand a dog’s macro-expressions, which are much more obvious and last longer that a split second. These include: baring teeth, doggy grin, helicopter tail, lowered head with crouched body, play bow, tucked tail, wigging body, raised hackles, rolling over and wrinkled muzzle among others. R33

​Never punish a dog for communicating. Instead, focus on preventing problems and addressing their root causes. If a dog feels stressed by other dogs, animals, people, situations or environments they must be able to handle – use desensitization, counter-conditioning and/or guided socialization to help them feel more comfortable. It’s just as important to protect the dog from dogs, people and experiences they should have to tolerate.

​If you notice signs of stress don’t let it pass. Immediately remove the dog from the situation – then you can decide whether you need to avoid the triggers or treat them with behaviour modification R21.

For those of us who truly love dogs, learning about and using micro-expressions to our advantage is about respecting our dogs and what they need to be healthy and happy. Our dogs have become master communicators and read us better than we read them R26. We owe it to them to learn their language as well, in order to strengthen our relationship. When our dogs realize that we understand them and have their backs, only then can they truly relax, enjoy their lives and not feel the need to lash out in order to protect themselves. We owe them the compassion to do what it takes to turn conflict and confusion into understanding and effective communication R22.

​R1: Yin, S. (2009). Low Stress Handling, Restraint and Behavior Modification of Dogs & Cats. CattleDog Publishing.
R2: Ekman, P. (2003). Emotions Revealed. Times Books.
R3: Bradshaw, J. (2011). Dog Sense. Basic Books.
R4: McConnell, P. (2002). The Other End of the Leash. Ballantine Books.
R5: Yin, S. (2009). Low Stress Handling, Restraint and Behavior Modification of Dogs & Cats. CattleDog Publishing.
R6: Overall, K. L. (2013). Manual of Clinical Behavioral Medicine for Dogs and Cats. Elsevier.
R7: Overall, K. L. (2013). Manual of Clinical Behavioral Medicine for Dogs and Cats. Elsevier.
R8: Rugaas, T. (2005). On Talking Terms with Dogs: Calming Signals. Dogwise Publishing.
R9: Horowitz, A. (2009). Inside of a Dog. Scribner.
R10: Donaldson, J. (2017). Culture Clash. Dogwise Publishing.
R11: McConnell, P. (2002). The Other End of the Leash. Ballantine Books.
R12: Donaldson, J. (2017). Culture Clash. Dogwise Publishing.
R13: Yin, S. (2009). Low Stress Handling, Restraint and Behavior Modification of Dogs & Cats. CattleDog Publishing.
R14: Bradshaw, J. (2011). Dog Sense. Basic Books.
R15: Horowitz, A. (2009). Inside of a Dog. Scribner.
R16: Rugaas, T. (2005). On Talking Terms with Dogs: Calming Signals. Dogwise Publishing.
R17: Horowitz, A. (2009). Inside of a Dog. Scribner.
R18: Bradshaw, J. (2011). Dog Sense. Basic Books.
R19: Overall, K. L. (2013). Manual of Clinical Behavioral Medicine for Dogs and Cats. Elsevier.
R20: Donaldson, J. (2017). Culture Clash. Dogwise Publishing.
R21: McConnell, P. (2002). The Other End of the Leash. Ballantine Books.
R22: Donaldson, J. (2017). Culture Clash. Dogwise Publishing.
R23: Horowitz, A. (2009). Inside of a Dog. Scribner.
R24: Bradshaw, J. (2011). Dog Sense. Basic Books.
R25: Yin, S. (2009). Low Stress Handling, Restraint and Behavior Modification of Dogs & Cats. CattleDog Publishing.
R26: Bradshaw, J. (2011). Dog Sense. Basic Books.
R27: Horwitz, D. F., & Mills, D. S. (2009). BSAVA Manual of Canine and Feline Behavioural Medicine (2nd ed.). British Small Animal Veterinary Association.
Detailed overview of canine sensory systems including vibrissae structure and function, highlighting their role in spatial awareness, hunting and emotional communication.
R28: Donaldson, J. (2017). Oh Behave! Dogs from Pavlov to Premack to Pinker. Dogwise Publishing.
Explores the consequences of suppressing natural canine communication and emphasizes the importance of humane training practices.
R29: McConnell, P. B. (2002). The Other End of the Leash: Why We Do What We Do Around Dogs. Ballantine Books. Discusses dog body language and communication, including why behaviours like growling are essential warning signals.
R30: Overall, K. L. (2013). Manual of Clinical Behavioral Medicine for Dogs and Cats. Elsevier Health Sciences.
Outlines the importance of treating the emotional and environmental root causes of behaviour issues rather than simply managing symptoms.
R31: Laurette. NJ. & Ceci.Greg. Blueprint To A Happy Dog. (2019). Canine Communication Styles. https://dogtrainingcareers.com/product/blueprint-to-a-happy-dog/
R32: Ciribassi, J. (2012). Forget dominance: Fear-based aggression in dogs. DVM360. Retrieved from https://www.dvm360.com/view/forget-dominance-fear-based-aggression-dogs
R33: American Kennel Club. (n.d.). How to read dog body language. American Kennel Club. Retrieved August 16, 2025, from https://www.akc.org/expert-advice/training/how-to-read-dog-body-language/

Photo By Maria Kemmett

By Norma Jeanne Laurette ​

​The vagus nerve plays an important role in helping the body shift between stress and calm. In dogs, this can be especially relevant when we are looking at anxiety, over-arousal, reactivity, fear, and the ability to settle after excitement or stress. When a dog struggles to calm down, recover, digest properly or feel safe, it’s worth looking at the nervous system as part of the bigger behavioural picture.
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The vagus nerve is a nerve that starts in the brain stem and travels down the neck to the chest and abdomen. It coordinates and regulates numerous body functions such as swallowing, gag reflex, brain to gut communication, digestion, breathing, heart rate, inflammation, immune response as well as the stress and relaxation response. In short, it functions as a major communication link that goes back and forth between the brain and the body (R3). It helps balance the sympathetic (fight or flight) and parasympathetic (rest and digest) branches of the nervous system (R7). The vagus nerve functions as the body’s re-boot system for a dog’s stress reaction.

​When we talk about resetting or supporting the vagus nerve in dogs, it’s not about reprimanding excitement or suppressing behaviour, it’s about the process of helping the dog’s nervous system return to balance after stress, excitement or overstimulation. When a dog becomes overwhelmed, its system can stay “switched on,” making it harder for it to calm itself, think clearly or recover from everyday triggers. A reset simply means creating the right conditions such as safety, predictability, reduced stimulation and gentle decompression time to allow the nervous system to naturally downshift. Over time, these experiences help improve resilience and the dog’s ability to calm itself when stressed (R1).

​When a dog is afraid, senses danger or is triggered to high arousal, the sympathetic nervous system is activated and triggers the fight or flight response. When this occurs the dog’s muscles tense, its breathing speeds up, heart rate increases and its mind becomes focussed on survival. It’s an innate control system that helps dogs react swiftly to perceived threats, but living in our human-centric world can cause it to get stuck in overdrive (R1).

​When the vagus nerve is activated, it switches the body into its parasympathetic nervous system, triggering the rest and digest state. When this system is engaged, the dog’s muscles relax, its breathing deepens, digestion improves, heart rate decreases, its mind becomes calm and the vagus nerve begins to heal itself (R4). In essence, when the vagus nerve is healthy and engaged, it functions to calm the fight or flight reflex, which makes it easier for dogs to recover from stress and anxiety, reduces inflammation and supports emotional resilience.
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Whether we’re dealing with an anxious, fearful, excitable, reactive or aggressive dog – the vagus nerve plays a big role in its ability to calm its state of arousal.  By understanding the vagus nerve and how to nurture healthy function, we can nurture a calmer, more resilient and healthier dog (R2).

​Constant stimulation can make it significantly harder for a dog to calm itself. When a dog is repeatedly exposed to noise, activity, training, social interaction, or ongoing environmental stimulation without adequate time to recover, its nervous system can remain in a prolonged state of arousal. Over time, this can reduce its ability to transition into calm, regulated states because the brain and body become conditioned to stay alert and reactive. Dogs require consistent downtime to allow their stress response system to reset. Without it, you will notice restlessness, reduced ability to settle, increased emotional reactivity or a dog that appears tired but still unable to relax. If the nervous system rarely gets a chance to fully down-regulate, calm behaviour becomes harder to achieve when needed most (R16). For more information about reactivity see my article Trigger Stacking & Canine Reactivity.

​What about genetically high-energy dogs and breeds? Can this constant stimulation harm the vagus nerve? The answer to this question is yes but not directly. Constant overstimulation keeps the sympathetic nervous system engaged while suppressing the parasympathetic nervous system (R2). Since the parasympathetic system’s calming affect is rarely exercised, over time the dog’s ability to calm itself is weakened.

Dogs that are constantly over-stimulated with games such as Frisbee, fetch, running, rough housing and erratic schedules can become locked into the same cycle of any adrenaline junkie. They only feel good when externally stimulated and never learn how to calm themselves (R5). Extended periods of overstimulation can lead to increased impulsivity and reactivity, inhibited rest and sleep cycles and poor emotional control when surprised by the unexpected.
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To prevent this problem it’s important to create an on/off switch for the dog’s energy by breaking up high-energy activities. This can be accomplished with settle down exercises (excite and settle), activities such as calm sniffing walks and self-control exercises such as down stays.

​Signs that a dog may be struggling to calm its nervous system can include pacing, whining and general restlessness or an inability to settle. Many dogs will pant even when they are not hot or physically active, shake off repeatedly or show clingy behaviour and difficulty relaxing when away from its guardian. Others avoid lying down or keep getting up, yawn frequently when not tired, or display lip licking or tongue flicking among other stress signals. You might also observe constant environmental scanning, sudden barking without obvious triggers or difficulty relaxing after exercise or excitement. Some dogs become more repetitive in their behaviours such as scratching or grooming more than usual, moving from room to room without settling or even freezing or shutting down (R17).

• A dog that can’t settle after visitors leave
• A dog that gets overexcited while playing and can’t calm down afterward
• A reactive dog that remains stressed long after seeing another dog
• A dog that pants, paces, whines or can’t relax in its own home even when nothing is happening
• A dog that needs decompression after every mildly stressful event
• A dog that remains hyper-alert or “on edge” for hours after a short walk or car ride
• A dog with chronic digestive issues such as intermittent loose stools, vomiting or loss of appetite when stressed, bloating or food sensitivities with no clear medical cause
• A dog that freezes, shuts down, or shows learned helplessness after overwhelming events
• A sound-sensitive dog with excessive startle responses or prolonged recovery from noises
• A dog that struggles to sleep or settle at night, frequently changing position, vocalizing or waking up restless despite physical exhaustion.
• A dog that over-reacts to minor triggers in daily life
• A dog with persistent shallow or rapid breathing even when lying down in a calm home environment or pants heavily indoors with no temperature or exercise cause.
• A dog that appears wired but tired with high overall energy and poor quality rest leading to crankiness and irritability
• A dog with compulsive behaviors such as excessive licking, tail chasing, walking in loops or pacing
• A senior or recovering dog that shows chronic neck/shoulder tension, sensitivity to touch around the head/neck
• A dog with clumsiness or poor coordination

For more information about compulsive behaviours see my article entitled OCD In Dogs. For other reasons dogs have trouble sleeping see Sleep Disorders In Dogs – Symptoms, Causes & Practical Solutions.

• Clingy
• Lip licking
• Tongue flicking
• Panting
• Pacing
• Shaking off
• Whining
• Yawning
• Repetitive behaviours such as scratching or grooming
• Avoiding lying down or constantly getting up
• Overreacts to mild stressors or everyday sounds
• Difficulty settling after stimulation
• Appears tense or guarded even in familiar environments
• Reduced ability to recover after exercise, excitement, play or training
• Avoids interaction or becomes socially withdrawn
• Restlessness after eating or during downtime
• Constant environmental scanning
• Moving from room to room without settling
• Sudden barking without obvious triggers
• Inconsistent focus during training
• Increased clinginess
• Freezing or sudden shutdown behaviour
• Lower threshold for frustration, quick to give up or disengage (R15)

Keep in mind that any of these behaviours could have other causes. If in doubt, an evaluation by a qualified and experienced positive canine behaviour expert is required. For information about becoming a behaviour expert visit our Certification page. For an international list of qualified, certified dog trainers/behaviour experts visit http://www.ipdta.org/.

​The vagus nerve’s ability to function effectively can be compromised by chronic inflammation, gut conditions, infections, prolonged stress or anxiety, physical and/or emotional trauma, poor diet, lack of sleep and erratic routines or schedules (R1) (R3) (R4). However, this damage can be reversed with a balanced and nutritious, natural diet, calming exercises and lifestyle changes, which allow the vagus nerve to heal. For information about nutrition see Canine Nutrition – Essential For Your Dog’s Health & Longevity and Canine Nutrition – Raw For Dogs.

​Without a healthy vagus nerve, a dog will have trouble shifting from a state of arousal to calm, making it difficult to recover (R1). When a dog can’t get out of the fight or flight mode it exacerbates problems such as health issues, emotional instability and chronic anxiety. (R4) (R8).

When a dog has difficulty calming itself it can lead to the following health issues:
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• Hormonal Imbalance: Affects metabolism, weight, coat and reproductive health (R10).
• Musculoskeletal Tension: Can result in repetitive injuries, stiffness, pain and tense neck, shoulders or back (R11).
• Gastrointestinal Issues: Resulting in nausea, diarrhea, constipation, colitis, gastritis or ulcers (R12).
• Suppressed Immune System: Causing allergies, skin, ear, urinary tract and respiratory infections, slower healing of wounds, increased parasite risk, allergies, autoimmune problems, chronic inflammation and cancer (R13).
• Cardiovascular Strain: Can lead to elevated heart rate and blood pressure, hypertension and heart disease (R14).

Healing the vagus nerve is not just about relaxation – it’s also about nurturing the foundation for physical, behavioural and emotional health for your dog. The most common methods for healing the vagus nerve include relaxation solutions, predictable and enjoyable routines, calm and positive training sessions that include self-control exercises, healthy nutrition and quality rest and sleep. For a complete guide to canine nutrition see my book entitled Dogs Examined.

Relaxation solutions such as canine enrichment options, pressure wraps, light massage or Tellington T Touch can help. Holistic anxiety supplemental aids are another option and include CBD oil (used with expert guidance), calming music, dog TV, calming scents, pheromone diffusers and safe natural supplements (R6). For more information about holistic stress supplements see my article Stress & Anxiety – Protecting Your Dog’s Health & Happiness.
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When a dog learns how to calm itself, the vagus nerve will heal and be able to work efficiently again. Understanding and healing the vagus nerve is not about interfering with a dog’s natural instincts or not allowing it to have fun, instead it’s about nurturing self-control through good physical and emotional wellbeing. By following the vagus nerve healing practices, you will reinforce your dogs health both physically and emotionally resulting in a calm, happy dog with superior self control.

• Predictable daily routines (consistent feeding, walks, rest times, etc.)
• Regular quiet rest periods with minimal stimulation
• No high-intensity exercise
• Canine enrichment options including natural foraging and sniffing walks
• Gentle, positive training with no pressure
• No verbal or physical corrections
• Soft, steady human interaction (calm voice, slow movements)
• Relaxation solutions including pressure wraps, light muscle massage or Tellington T Touch, gentle touch or calming contact if the dog enjoys it
• Safe, quiet spaces for decompression
• Reduce constant background noise and overstimulation at home
• Support rest after excitement (structured “wind-down” time)
• Avoid over-scheduling social interactions or training sessions
• Allow the dog choice and space in interactions (autonomy)
• Consistent sleep environment and undisturbed sleep
• Gradual exposure to stressors instead of flooding using desensitization and counter conditioning
• Protect the dog from stressors it should not have to tolerate (R18)

For more information about canine enrichment see my article Canine Enrichment For Dogs. For more information about autonomy see Why Dogs Need Freedom Of Choice and Autonomy & A Well Behaved Dog. For information about desensitization and counter conditioning see our book Blueprint To A Happy Dog.

What is the vagus nerve in dogs?
The vagus nerve is part of the nervous system that helps regulate stress, digestion and heart rate, and helps the body shift between stress and calm states.

What are signs of vagus nerve imbalance in dogs?
Signs of vagus nerve imbalance include stress and anxiety, difficulty settling and sleeping, behaviour problems, gastrointestinal dysfunction, respiratory and physiological arousal, cardiac, immune and inflammatory issues.

How do I calm my dog’s nervous system?
To calm the vagus nerve follow a consistent routine, maintain calm, low stress environments and interactions, relaxation after excitement, gentle touch and massage, canine enrichment, a natural, balanced diet and additional therapies.

Can stress affect a dog’s nervous system long-term?
Yes. Chronic stress can make it harder for dogs to return to a calm baseline and can lead to long-term health and behaviour problems.

Does exercise help regulate the vagus nerve in dogs?
Yes, but it should be balanced with rest and not over-stimulating activity.

What is the fastest way to calm an anxious dog?
A quiet space, reduced stimulation and calm human presence with someone they know and trust.

Can routine improve a dog’s behaviour and stress levels?
Yes. Predictable routines help dogs feel calmer and safer.

Do dogs need downtime to stay calm?
Yes. Downtime is essential for nervous system recovery and balance.

Can overstimulation make dogs anxious?
Yes. Too much stimulation can keep dogs in a heightened state of arousal.

Does sniffing help calm dogs?
Yes. Sniffing activities support relaxation and help lower arousal.

​Healing the vagus nerve offers a powerful, scientifically proven pathway to helping dogs regulate stress, recover from anxiety, return to good health and a balanced emotional state. By supporting the body’s natural parasympathetic “rest-and-digest” nervous system, we can shift our dogs out of the chronic fight-or-flight pattern and into calmer, more resilient behaviour and emotional wellbeing. This approach changes the way we look at reactivity, not as disobedience, but as a physiological state that can be gently and humanely guided back to equilibrium.
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Through carefully applied techniques, guardians can help strengthen a dog’s vagal tone over time for improved quality of life. Healing the vagus nerve is not a quick fix, but instead a compassionate program for restoring nervous system balance and helping our dogs feel safe and calm in our human-centric world.

​(R1) Porges, S. W. (2011). The Polyvagal Theory: Neurophysiological Foundations of Emotions, Attachment, Communication and Self-regulation. W. W. Norton & Company. Describes how the vagus nerve regulates the autonomic nervous system. Describes how the vagus nerve regulates the autonomic nervous system.
(R2) Dana, D. (2018). The Polyvagal Theory in Therapy: Engaging the Rhythm of Regulation. W. W. Norton & Company. A practical guide to applying vagal theory for emotional health and behavior.
(R3) Rosenberg, S. (2017). Accessing the Healing Power of the Vagus Nerve: Self-Help Exercises for Anxiety, Depression, Trauma and Autism. North Atlantic Books. Offers clear, simple exercises for vagus nerve stimulation.
(R4) Navazesh, M., & Kumar, S. K. S. (2008). Neuroanatomy and Physiology Relevant to Vagal Nerve Function. Journal of Oral and Maxillofacial Surgery, 66(4). Summarizes the anatomical pathways of the vagus nerve and its systemic roles.
(R5) Overall, K. L. (2013). Manual of Clinical Behavioral Medicine for Dogs and Cats. Elsevier Health Sciences. Includes protocols for calming dogs and teaching relaxation to reactive animals.
(R6) Levine, P. A. (2015). Trauma and Memory: Brain and Body in a Search for the Living Past. North Atlantic Books. Discusses how body-based calming aids, touch and gentle pressure can support nervous system healing.
(R7) O’Neill, D. G., & Hall, E. J. (2020). Vagus nerve function and dysfunction in dogs. Veterinary Record, 186(7), 217–222. This article explains the vagus nerve’s role in regulating heart rate, digestion, breathing and its dual influence on the sympathetic and parasympathetic nervous systems in dogs.
(R8) McGonigal, K. (2015). The Upside of Stress: Why Stress Is Good for You and How to Get Good at It. Avery. Explores how chronic stress impacts health through physiological pathways, including the vagus nerve.
(R9) Porges, S. W. (2017). The Pocket Guide to the Polyvagal Theory: The Transformative Power of Feeling Safe. W. W. Norton & Company. Explains how the vagus nerve regulates behavior and stress responses in mammals.
(R10) Beerda, B., Schilder, M. B. H., Bernadina, W., van Hooff, J. A. R. A. M., & de Vries, H. W. (1999). Chronic stress in dogs subjected to social and spatial restriction. I. Behavioral responses. Physiology & Behavior, 66(2), 233–242. Shows chronic stress impacts endocrine balance in dogs.
(R11) Landsberg, G. M., Hunthausen, W., & Ackerman, L. (2012). Behavior Problems of the Dog and Cat (3rd ed.). Saunders Elsevier. Covers musculoskeletal tension linked to stress and anxiety behaviors.
(R12) Overall, K. L. (2013). Manual of Clinical Behavioral Medicine for Dogs and Cats. Elsevier. Discusses stress-related gastrointestinal issues in dogs.
(R13) Mormède, P. andanson, S., Aupérin, B., Beerda, B., Guemene, D., Malmkvist, J., Manteca, X., Manteuffel, G., Prunet, P., & Van Reenen, C. G. (2007). Exploration of the hypothalamic–pituitary–adrenal function as a tool to evaluate animal welfare. Physiology & Behavior, 92(3), 317–339. Reviews stress-induced immune suppression.
(R14) Dreschel, N. A. (2010). The effects of fear and anxiety on health and lifespan in pet dogs. Applied Animal Behaviour Science, 125(3-4), 157–162. Discusses cardiovascular strain and related health risks in chronically stressed dogs.
(R15) Overall, K. (2013). Manual of Clinical Behavioral Medicine for Dogs and Cats. Elsevier. Provides a clinical framework for understanding behavioural signs associated with autonomic arousal, stress responses, and regulation difficulties in companion animals.
(R16) Horowitz, A. (2014). Decoding Your Dog. Scribner. Explains how environmental stimulation, arousal states, and learning history influence a dog’s ability to regulate behaviour, settle, and recover from excitement or stress.
(R17) Yin, S. (2009). Low Stress Handling, Restraint and Behavior Modification of Dogs & Cats. Cattle Dog Publishing. Provides behavioural indicators of stress, arousal, and difficulty returning to a calm baseline in dogs.
(R18) Moberg, G. P., & Mench, J. A. (2000). The Biology of Animal Stress: Basic Principles and Implications for Animal Welfare. CABI Publishing. Explains how stress load, predictability, and recovery time influence physiological and behavioural regulation in animals.

​Photo By Norma Jeanne Laurette