Understanding the posttraumatic stress continuum in dogs

For the veterinary professional, the clinical focus has historically prioritized physical trauma. However, as Franklin McMillan, DVM, DACVIM, DACAW, argued at the 2026 Western Veterinary Conference (WVC 2026) in Las Vegas, Nevada, the emotional scars left by psychological trauma are just as real. The challenge for the modern practitioner lies in recognizing these invisible wounds in patients who lack the verbal capacity to communicate their trauma.

The mechanics of a psychological wound

McMillan defined psychological injury through the lens of failed homeostasis. Under normal conditions, a mammal experiences a stressor and eventually returns to a balanced state. However, in cases of severe, repetitive, or prolonged adversity, this return to homeostasis fails to occur. Instead, the patient remains in a state of red alert, where "the mind and body continue to function as if the trauma were continuous in daily life,” he said.¹

The spectrum of fear from normal to pathological

A primary theme of the lecture was the distinction between adaptive, learned fear and pathological trauma. McMillan posited that these do not exist as distinct categories but rather on a continuum.

"Responses to adversity exist on a continuum. There is no distinct line between nonpathological, learned fears and psychological trauma," he said.

He explained that an adaptive fear, such as a dog avoiding a basement where it was once trapped, is a survival-based response to a specific stimulus. In contrast, pathological trauma involves harmless stimuli triggering full-scale physiological and escape-avoidance responses.¹

When these excessive fear responses interfere with normal, adaptive behaviors, such as a dog refusing to leave the house or cowering at the sound of a dropped coin, the fear has transitioned into the realm of psychological injury, McMillan explained.¹

The communication barrier

The communication barrier remains the most significant hurdle in veterinary behavioral health, according to McMillan. "The single biggest challenge for understanding psychological trauma in animals is that we can't talk to them," he said. This diagnostic gap restricts access to subjective symptoms, such as flashbacks or nightmares.¹

To bridge this gap, veterinarians can look toward pediatric psychiatry. Preverbal or traumatized children often cannot describe their internal state, leading clinicians to rely on observable criteria such as hyperarousal, hypervigilance, and exaggerated startle responses. By focusing on these visible markers, veterinarians can diagnose posttraumatic stress (PTS) without needing a verbal history from the patient, McMillan explained.¹

PTS vs PTSD

A significant portion of the session was dedicated to trauma nomenclature. Although posttraumatic stress disorder (PTSD) is the standard clinical term in human medicine, McMillan suggested that PTS is a more inclusive and practical label for veterinary use. In the human sector, the distinction between PTS and PTSD often serves as a threshold for insurance or disability claims.¹

In veterinary medicine, this rigid diagnostic threshold offers no clinical advantage. McMillan argued that classifying only the most severe cases as "disorders" risks denying care to animals that fall just below the diagnostic threshold but still suffer significant impairment. He said that by utilizing a PTS continuum—categorizing cases as mild, moderate, or severe—practitioners can ensure that every animal receives the appropriate level of intervention.¹

Resilience and recovery

Despite the gravity of psychological trauma, there is a strong element of resilience in mammals. He explained that data indicate that approximately 75% of individuals exposed to traumatic events are resilient and eventually recover. For the remaining 25%, however, the fear generalizes until “the world itself becomes a threat.”² These patients display an elevated baseline of arousal, remaining behaviorally primed for another stressful event at all times. The ultimate goal for the veterinarian is to recognize these signs early, providing the behavioral and pharmacological support necessary for these animals to regain a life of enjoyment, McMillan said.¹

References

1. McMillan FD. Posttraumatic stress in dogs. Presented at: 2026 Western Veterinary Conference; February 15-18, 2026; Las Vegas, NV.
2. McMillan FD, ed. Mental Health and Well-Being in Animals. 3rd ed. Wiley-Blackwell; 2024.