How do you know if your dog is stressed? Experts have identified some of the anxious behaviors your companion dog may exhibit:
- Crying or whining
- Inappropriate elimination
- Looking away from a threat
- Loss of appetite
- Pinning ears back
- Self-directed behaviors such as flank sucking, tail chewing, tail chasing, self-nursing, and excessive licking, chewing of the feet or nails, scratching or rubbing
- Tucking tail
While many of us think of stress in terms of the psyche, it is actually more complicated than that.
ACUTE OR CHRONIC STRESS?
First, stress is categorized as either acute or chronic.
Acute stress is modulated by the sympatho-adreno-medullary (SAM) axis. It is commonly known as the “fight or flight” syndrome and lasts for a very short period of time. Indications can include increased blood pressure and heart rate.
Chronic stress is a slower response to a stressor that manifests within several minutes to days after the initial activation. Chronic stress is regulated by the hypothalamic-pituitary-adrenal (HPA) axis. Through a complex reaction in the body, hormones such as glucocorticoids, cortisol and corticosterone are produced and released. Eventually, these hormones can negatively affect metabolism and immune function, as well as potentially impact thyroid function and the reproductive system.
PHYSIOLOGICAL OR PSYCHOGENIC?
Now that we have the biological reaction to stress, we need to categorize what initiates the stress: physiological or psychogenic.
Physiological stress is due to such issues as trauma, surgery, injections including vaccinations, sex hormonal and other hormonal changes, systemic illness and shock.
Psychogenic stress is how the body responds to emotional or mental stressors and can be further classified. Negative psychogenic stress could manifest from separation anxiety in dogs. Alternatively, positive psychogenic stress may result from the reunion with another companion pet or parent, familiar relative or friend. In terms of psychogenic stress, the concern is that these emotional or mental stressors if ongoing could manifest into a physical illness.
Vaccinations are interesting to assess in terms of physiological and psychogenic stress. For instance, the “fight or flight” reaction can actually be immune enhancing and help receptivity to the vaccine. On the flip side, psychogenic stressors elicit a poorer antibody response, which means the uptake of the vaccine might be less effective than it could have been.
MEASURING PSYCHOGENIC STRESS IN DOGS
Measuring cortisol in blood and in particular, saliva, has become popular these days in figuring out the stress response in dogs and other species.
One study simulated a thunderstorm in a home setting. Saliva samples were collected to measure cortisol levels before, as well as 20 and 40 minutes after the exposure. During the thunderstorm, dogs presented classic signs of fear such as pacing, whining or hiding. Their cortisol levels increased 207% and were still elevated 40 minutes after the loud noise. Researchers also discovered that the dogs that lived with other dogs had less of a reaction and recovered to baseline more rapidly.
Another study compared aggressive dogs to non-aggressive dogs. The aggressive dogs had significantly lower serotonin and higher cortisol levels in their blood than the non-aggressive dogs.
Cortisol was higher in Cavalier King Charles Spaniels that exhibited fear-related avoidance behaviors more so than in puppies that did not have the same observed fear-related response. This study also demonstrated that behavioral responses differed between Yorkshire Terriers, Cavalier King Charles Spaniels and German Shepherds.
OTHER STRESS MEASUREMENTS
Immunoglobulin A (IgA) measurement can be used to determine the stress level in humans. In dogs, we can find out their IgA level either through blood or saliva. However, there is concern that it may not be a reliable indicator of the stress level in dogs since IgA levels, like cortisol, vary during the day and may not differentiate between psychogenic and physiological stress.
Another test looks for an elevated neutrophil:lymphocyte (N:L) ratio. The benefit of this ratio is that it varies less than cortisol levels. This test requires a blood sample and is merely a qualitative assessment affected by other health factors. Other issues with the ratio are similar to IgA measurement; we are unsure if the stress is psychogenic or physiological and it is not as well understood as cortisol.
Positive and negative psychogenic stressors can result in heart rate increases. Monitoring heart rate and its variability is a more effective indicator of acute stress in dogs.
WHEN PSYCHOGENIC STRESS CAUSES LONG-TERM PHYSIOLOGICAL HEALTH CONDITIONS
As discussed above, fear and anxiety caused by stress can impact bodily systems such as the metabolic, glandular and immune.
But, do we know the exact long-term diseases that can ensue in dogs?
We could not find any definitive studies that linked stress to one particular disease in dogs, but experts assert that many affected species and individuals develop diseases and have shortened lifespans.
For instance, one study found that people with a stress-related disorder have a higher incidence of autoimmune disease like rheumatoid arthritis or multiple sclerosis than those without one.
Dr. Nancy Dreschel of Pennsylvania State University surveyed 721 companion dog parents whose dogs had passed, and found:
- If a dog was considered “well-behaved” by the pet parent, that positively correlated with lifespan. So, dogs lived longer.
- Dogs with extreme non-social fear and separation anxiety were found to have increased severity and frequency of skin disorders.
- Fear of strangers was found to be related to a significantly shortened lifespan.
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