The Myth of the Three-Day Stress Cycle: How Stress Really 'Sticks' to Our Dogs

When we talk about stress "sticking around" in an animal’s system, we are referring to glucocorticoids—the stress hormone most commonly known as cortisol. To truly understand how stress affects our dogs, let's look at the science behind the stress response.

We define stress as a natural, physiological, and psychological response to perceived challenges or threats to an animal's normal state. Not every challenge is harmful! According to researcher Bruce McEwen, stress can be broken down into categories:

• Good Stress (Eustress): A challenge that is not unpleasant, such as learning a new trick, playing, or exploring a safe area. The animal copes and grows.

• Tolerable Stress: Unpleasant, but the animal is able to cope and recover.

• Toxic Stress: The animal cannot cope with or escape the stressful situation.

When your dog's brain detects a stress/a threat, two primary systems activate instantly:

• The Hypothalamic Pituitary Adrenal Axis(HPA Axis): A complicated sequence that ultimately releases the stress hormones, including cortisol.

• The Sympathetic Nervous System: This system releases norepinephrine and epinephrine (adrenaline), plunging the animal into fight or flight.

These systems flood the dog's body, causing physiological changes like increased heart rate, rapid breathing, and a surge in blood sugar. This prepares them to face or flee the perceived challenge.

How Long Does Cortisol Stay in the System?

For a healthy, non-stressed dog? Not long.

In a healthy system, the body triggers a "shut-off valve" (a negative feedback loop) once cortisol levels peak. Studies show that a normal dog typically reaches this peak and begins cycling stress hormones out within 15–30 minutes.

So, does stress stay in the system for three days? For healthy dogs, absolutely not.

The Exception: Chronic Stress & The Three-Hour Cycle

The simple answer above changes dramatically when a dog is under chronic stress. Chronic stress is a prolonged state of strain caused by ongoing, inescapable stressors in the dog’s life.

Dogs under chronic stress have a higher baseline level of cortisol.

More importantly, it takes them much longer to trigger the "shut-off valve." Studies show these dogs generally take around 3 hours to cycle stress hormones out of their system.

The Real Reason Stress Lasts: Sensitization

While the actual stress hormone (cortisol) is cleared within hours, the effects of stress can linger for days, weeks, or even indefinitely. This is due to a neurological concept called sensitization.

Sensitization refers to a process where repeated or highly traumatic exposure to a stimulus leads to an increased responsiveness to that stimulus over time. This increased sensitivity can last up to several weeks.

Even more troubling is Cross-Sensitization. Research (often using models like "inescapable shock" that leads to learned helplessness) shows that an animal isn't just sensitized to the original trigger. Instead, the entire system becomes hyper-vigilant:

Any other aversive or stressful stimulus will also trigger this heightened sensitivity and anxiety, even without repeated exposure to that new trigger.

If a dog is experiencing cross-sensitization, they will experience a heightened, anxious response to stress and aversive stimuli for up to 10 days, sometimes longer. This prolonged state of anxiety contributes to chronic stress, which, in turn, prolongs the cortisol cycle.

No, the cortisol doesn't stay in the system for three days, but the complicated combination of stress pathways and cross-sensitization can result in a dog who is stressed out for not just three days, but possibly weeks. Some animals may never be able to get out of the loop at all.

What Can We Do to Help?

The good news is we have the tools to help reduce toxic stress and lower their baseline anxiety:

• Stop Aversives: Eliminate the use of training methods and tools that rely on repeated punishment or aversive stimuli.

• Manage Exposure: When training, always create exposure scenarios at a manageable level for your dog. Never allow your dog to go "over threshold" (past the point where they can think and cope).

• Prioritize Recovery: Recognize and respect your dog's need for time to de-stress. Now that you know how long stress truly affects the system, give them appropriate rest and enrichment.

Resources:

Garcia, Arantxa, Octavi Marti, Astrid Valles, Silvina Dal-Zotto, and Antonio Armario. “Recovery of the Hypothalamic-Pituitary-Adrenal Response to Stress: Effect of Stress Intensity, Stress Duration and Prevention Stress Exposure.” Neuroendocrinology 72, no. 2 (August 2000): 114–25.

Belda, X., Rotllant, D., Fuentes, S., Delgado, R., Nadal, R., & Armario, A. (2008). Exposure to severe stressors causes long‐lasting dysregulation of resting and stress‐induced activation of the hypothalamic‐pituitary‐adrenal axis. Annals of the New York Academy of Sciences, 1148(1), 165-173.