Pain, simply defined, is an aversive sensory experience caused by an unpleasant or harmful stimulus, associated with actual, or in response to potential, tissue damage. Acute pain is typically pain that lasts a short period of time and subsides after the inflammatory and healing processes have completed. Chronic pain is more complex in nearly all respects as compared to acute pain. Chronic pain can occur with or without an initial acute injury, can become progressively worse, can occur intermittently and outlasts the usual inflammatory healing process. Some types of pain, particularly that which is chronic in nature, is a maladaptive process caused by a broad range of conditions that can affect any organ or tissue that possesses nerve endings.
Pain can inhibit normal behaviors and precipitate abnormal behaviors and can greatly interfere with the quality of life for both companion canines and their owners (Downing, 2011& 2013, and Davis, et al., 2019). Both acute and chronic pain, can be easily overlooked as companion animals because they are masters at hiding pain, and unlike their human counterparts, are unable to self-report their pain. Because of this, pain can often be overlooked or attributed to the aging process in companion animals, making it even more important to understand the relationship between chronic pain and behavior.
Research has shown that chronic pain is correlated with emotional and cognitive changes, furthermore, that chronic pain can fundamentally change the brain on both a structural and functional level, contributing to the development of, or increase in emotional and cognitive issues in both humans and animals (Yang & Chang, 2019). Brain regions involved with pain processing are similar to those involved with behavior, and the structural and functional changes in those areas is associated with the progression of pain from acute to chronic (Yang & Chang, 2019). Specifically, important structures associated with chronic pain are also responsible for mediating or controlling behavior in one respect or another.
Recent studies have shown that molecular and cellular changes in these critical brain areas of animals with chronic or persistent pain led to marked behavior changes including an increase in anxiety behaviors, and decrease in both learning ability and memory (Mutso, et al., 2012). Chronic pain related changes in these brain areas are critically associated with an increase in anxiety related behaviors and other emotional and cognitive difficulties, like those responsible for flight or fight responses, and for the regulation of drives and motivation, as well as fear, aggression and avoidance behaviors (Goddard, 1964).
Chronic pain can be associated with changes in the brain in not only function but also structure as compared to acute pain. Research has demonstrated that chronic pain changes brain activity, specifically how pain is processed. With chronic pain, processing in the brain shifts from typical pain areas responsible for addressing acute pain, to areas typically implicated and responsible for emotions and behavior with chronic pain states (Ahmed, 2013). Chronic pain states have been associated with brain activity in areas that are normally considered to control or regulate emotion, motivation, and behavior, making it extremely important for owners to address any behavior changes, however slight.
Medical issues, particularly those involving chronic pain, may contribute to behavior issues or increase existing behavior problems in companion canines (Becker, 2015). While veterinarians are able to identify some pain responses, it is often the case that addressing physical symptoms of pain occurs well after the disease has progressed, and in some cases, well after pain related behavior changes have surfaced. Often behavior changes are the first sign of an underlying clinical problem like those involved in chronic pain states (Roshier & McBride, 2012).
Pain related behavior changes can take on many forms, and owners may note changes suddenly, as well as gradually. They can manifest as changes in attitude, mentation or demeanor, as development or increase in fearful, anxious or stress behaviors, avoidant behaviors, or increase in hyperactivity, or heightened sensitivity and cautious behaviors (Lopes Fagundes, et al., 2017 and Balakrishnan & Benasutti, 2019). Some of the most common pain related behavior changes are seen as changes in demeanor, including fear and aggression, toward owners or other pets in the home, as well as increase in guarding behaviors toward owners or other pets, such as growling when approached, or increase in fighting among housemates (Balakrishnan & Benasutti, 2019). While behavior changes can occur suddenly or gradually, it is important to understand the potential for these changes to be in response to chronic pain. Companion animals experiencing severe or chronic pain are often found to be anxious and restless and can become increasingly protective, unmanageable or aggressive, while others can become submissive or depressed (Wiese, 2018).
Chronic pain related behavior changes are not unique to older or aging companion animals, with more chronic pain conditions and diseases recognized more and more in juvenile animals, it is important for owners to address and behavior changes regardless of age. Chronic pain related behavior changes are also not unique to companion canines. Recent research investigating the relationship of chronic pain and behavior issues in felines found that declawing surgeries which resulted in development of chronic back pain increased the incidence of unwanted behaviors in felines (Martell-Moran, et al., 2018). When dealing with our feline friends, it is important to understand that changes in behavior associated with chronic pain can be even more subtle than with canines, and that even more often, feline behavior changes are mistakenly attributed to age (Gottlieb, 2018). For felines, common signs of chronic pain can include both an increase or decrease in normal grooming activity, inappropriate elimination, or eliminating outside of the litter box, increase in hiding behaviors, or more marked emotional changes like increase in fear or aggression. For felines, many common medical conditions can result in chronic pain states including typical urological issues including stones and crystals, or diabetes, as well as many other disorders that may have few overt clinical signs but cause chronic pain states (Gottlieb, 2018).
Behavior changes due to chronic pain can be highly individual, and can range from subtle non-specific changes to more overt changes including reduced general activity and reduced sociability to increased incidence of anxious or aggressive behavior; behavior displays may be intermittent and dependent on the severity of pain at the time the behavior is displayed (Belshaw & Yeates, 2018). However, because companion animals are unable to effectively describe their own pain, it is even more important for owners to adequately investigate behavior changes.
What can owners do?
Learning to identify physical changes, along with behavioral changes can help owners potentially identify chronic pain diseases or illnesses earlier in their progression. Recognizing chronic pain can be challenging, particularly because animals are adept at hiding pain, and not all behavior changes are recognized as a potential sign of chronic pain. Therefore, it is vitally important for owners to be mindful of even subtle or intermittent changes, both physical and behavioral. Owners are the best advocates for their pets and being able to articulate what is normal or abnormal for their individual pet will help veterinarians better identify potential issues.
Owners can help facilitate discussions with their vets by keeping a good log or history of any physical or behavioral changes they are noticing, including things like changes in demeanor, energy level or exercise, any changes to eating or elimination patterns as well as any behavior changes however slight or seemingly gradual. Owners can help identify overall changes in behavior in terms of changes in attitude and mood, as well as identifying potential behaviors associated with chronic pain states like frequency of vocalizations or displays of discomfort, willingness to engage or play with owners, new fears or sensitivities, increased anxiety or aggression, or changes to overall relationship dynamics between people or other pets. Owners can also take note of physical changes, including changes in posture or physical capabilities, or any new sensitive or painful areas of the body.
Owners who suspect chronic pain related behavior issues can seek out behavior professionals who can work collaboratively with veterinarians. Bringing in a behavior professional can help bridge the gap between veterinary treatment for the underlying chronic disease, and behavior management for the home environment to better help owners manage both the physical and behavioral aspects of chronic pain. Owners can find reputable behavior professionals through the International Association of Animal Behavior Professionals (https://m.iaabc.org/consultant/) or American Veterinary Society of Animal Behavior (https://avsab.org/directory/) and the Association of Animal Behavior Professionals (https://www.associationofanimalbehaviorprofessionals.com/directory).
Author: Nicole Ribeiro, MBM
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