DEBRA F. HORWITZ

Veterinary Behavior Consultations, St. Louis, Missouri, USA

The concept of mental health in animals has not necessarily been an important variable in understanding the animals we interact with and in establishing their overall welfare and well-being. Early studies of the behavior of differing species focused on how certain traits were passed along to offspring and Darwin was the first to correctly posit that the desire for reproductive success, i.e., putting one’s genes into the next generation, drove many changes in both form (how the organism looked) and function (what the animal did). Further studies discovered that certain behaviors were not affected by environmental circumstances and occurred regularly in response to very specific cues. These were termed instincts, which refers to behaviors that appears in a fully functioning form the first time they are performed – where no learning is required (Alcock, 1993). However, other behaviors are the result of learning: the modification of behavior in response to specific circumstances and information from other individuals and the environment. Over time and further study this came to be formulated into ‘learning theory’, which comprised definitions and examples of how individuals (both people and animals) learn new tasks (Schwartz and Robbins, 1995). Finally, there are behaviors that occur because they are a normal part of the animals’ behavioral repertoire. For example, obtaining food may occur due to information from scent or sight, determining where the food is readily available, and so on. Given that so many companion animals live in our homes, their mental health has taken on a greater meaning.

1.2 What is Behavior and What is Mental Health?

1.2.1 Behavior

Behavior can be broadly defined as what an animal or person does and how they function within their environment. One’s behavior is influenced and affected by the individual’s genetics, environment, early experiences, social experiences, and encounters with animate and inanimate objects. The accumulating knowledge in this area led to the creation of the field of ethology, which seeks to understand the adaptive function of animal behavior and behavioral characteristics. Ethological studies now widely utilize the ethogram – a catalog of individual or species behaviors that may include the frequency and duration of each behavior.

Ongoing behavior is usually influenced by its consequences: if the outcome is one that the animal finds favorable the behavior is likely to occur again, and, conversely, if the outcome is something less than favorable or even adverse then the behavior is less likely to occur in the future (at least in that circumstance). This is all controlled by learning, whether through interactions with the environment or with other individuals. Some behaviors are more highly motivated and thus more likely than others to occur; these behaviors are more important to the animal’s normal behavioral patterns and may be difficult to deter. Additionally, changes in the environment, social organization, illness, anxiety, and stress can result in the animal showing alterations in their behavior.

1.2.2 Mental health

Assessing the mental health of animals is a relatively recent development and has been utilized more consistently in the past 20 years in companion animals. Prior to that time, what was discussed was the welfare of those animals in human care. The most commonly used method – originally developed for use in farm animals – is known as the Five Freedoms (Farm Animal Welfare Council, 2009) and includes the following:

Another measure is the United States Department of Agriculture’s Six Elements to Psychological Well-being in Captive Animals (Kulpa-Eddy et al., 2005), which has recently been clarified and updated. Additional approaches include quality-of-life (QOL) assessments and mental health wellness as described by McMillan (2002), which focus on a balanced QOL by recognizing both pleasant and unpleasant feelings in the areas of social relationships, mental stimulation, health, food, stress, and control/predictability while incorporating differences in personal preferences. Others define QOL as the combinations of the animal’s feelings, physical state, and its ability to satisfy its nature (Wojciechowska and Hewson, 2005).

Merriam-Webster (2019) defines mental health as

As can be seen, this definition takes in most of the items discussed in the Five Freedoms and QOL definitions.

1.2.3 How do stress and anxiety factor into mental health and behavior?

At its simplest, anxiety is the anticipation of danger or threat. Sources of anxiety in companion animals can be anything from being left home alone for long periods of time, uncertain social interactions with other animals or humans, the inability to engage in normal species-specific behaviors, and lack of control and predictability in daily life. However, in many cases the source of anxiety may not be readily identifiable.

Anxiety can cause stress, which is a protective mechanism. When an organism perceives a threat – a stressor – activation of the hypothalamic–pituitary–adrenal (HPA) axis and sympathetic nervous system occurs, engaging the body’s ‘fight-or-flight’ response (Mills et al., 2013). This stress response has physiological, behavioral, and psychological components and enhances the animal’s ability to perceive, evaluate, and choose the correct response to alleviate and recover from the threat. Not all stress is problematic if it is short term and the animal is able to return to normal baseline functioning. If this is not possible, the animal is experiencing ‘distress’, the mental state that occurs when the circumstances overwhelm the animal’s ability to cope with the situation (see also Chapter 11, this volume). Distress is highly individual: that which is distressing to one animal may not be distressing to another. Chronic distress can occur with frequent exposure to stressors or unrelenting exposure to a stressor that never abates and acts over an extended period of time. This can cause chronic dysregulation of the HPA axis and excessive corticosteroid exposure, which may then lead to changes in learning and memory and adversely affect the animal’s overall health. Chronic stress can be due to a health issue, social conflict with other animals in the home, social isolation, and many other causes.

On its own, anxiety and its accompanying physiological changes are probably not pathological when short-lived, but chronic anxiety can lead to chronic stress. Anxiety, like stress, can become a chronic state and compromise the health, welfare, and lifespan of the individual (Dreschel, 2010). Responses to anxiety-provoking stimuli are likely influenced by early learning, negative experiences during development, and the individual’s genetics (Mertens and Dodman, 1998). If the same experience is repeatedly encountered, anxiety and apprehension may occur through sensitization, potentially resulting in enhanced responses. Stimulus intensity and frequency of encounters may compound the response and various associative processes may accelerate acquisition of responses (Levine, 2009). Because of this, we must acknowledge and accept that animals can and often will refuse to perform behaviors that cause them distress, fear, or pain, and forcing animals to do these things is unacceptable. Therefore, to provide optimum health and welfare for all pets we should include anxiety and stress as adverse states that can affect the mental health of companion animals.

1.3 The Intersection of Mental Health and Behavior

If behavior is what the animal does, then mental health is how the animal ‘feels’. However, the behavior displayed may or may not accurately represent emotional states or the animal’s mental health. The meaning of the behavior is based on the animal itself and its early experiences, socialization, genetics, training, and traumatic events (see Chapter 14, this volume).

The disciplines of veterinary behavior and mental health care in animals overlap at many points. Both are concerned with the ability of animals to experience fulfilling and clear social relationships, perform and engage in normal species behaviors, have appropriate outlets for mental stimulation, be provided with appropriate and timely physical health care, and receive a diet that meets their needs. Additionally, both disciplines recognize that all animals need some control and predictability to feel behaviorally and mentally healthy (see Chapter 6, this volume). Animals should be allowed to say ‘no’; behaviorists and mental health practitioners agree that animal caregivers must respect an animal’s decision not to engage in a particular behavior or activity and help the animal learn and understand why, when the behavior is necessary, it must be performed. Furthermore, the disciplines of behavior and mental health care also intersect with regard to the animal’s response to and ability to function when the environment or some other aspect of life is stressful.

The point where the two disciplines can seem to work in opposing directions often depends on the how a pet owner interprets specific behaviors – as good or bad – and attaches importance to the animal’s mental health. Consider a dog whom the owner wants to take running with them every day. After several months the dog begins to hide when it is time to go running. The owner could be upset since she feels that taking the dog on a daily run provides the exercise and mental stimulation essential for the animal’s good mental health. However, the dog may find running unpleasant, perhaps because of such things as stress when encountering other dogs, frustration from the inability to explore and sniff the environment, or pain from osteoarthritis or other physical disorders. It is entirely possible that in this example something that the owner sees as an improper behavioral response to her efforts to benefit her dog’s mental well-being is actually the dog’s attempt to protect itself from things which can harm this well-being.

Another example is a cat who is friendly to family members but runs and hides whenever company comes to the house. The family may see this as undesirable behavior: being friendly to them but unfriendly to others may be insulting and upsetting to owners who expect the cat to behave differently. However, the cat may not have been sufficiently socialized to people early in life and now finds strangers frightening and stressful. By seeking a safe hiding place stress and anxiety is alleviated, which is beneficial to the cat’s mental health. The owner must respect this need to escape; after all, we do not expect every person to be comfortable around every other person.

The divergence of the two disciplines is perhaps clearest in cases where an animal with excellent mental health is performing a normal and natural behavior that the owner finds unacceptable. It must be kept in mind that the evolutionary history of companion animals spans tens of thousands of years, and keeping pets inside human homes is, relatively speaking, a very recent development. It is no surprise, then, that there are numerous normal behaviors which companion animals perform that may not be suitable for the household, and are unwanted by caregivers. These include marking with urine or claws, exploratory chewing, climbing, and rambunctious activities that result in damage to the owner or her possessions. These behaviors are commonly unaccompanied by impaired mental health and are often presented to both veterinary behaviorists and trainers as behavior problems when in reality they might just be a result of insufficient outlets for normal species-specific behaviors, inadequate attention to normal animal needs, or unrealistic expectations. In other cases, the animal may be frustrated by the inability to meet its daily need for mental stimulation, social interaction, safety, and control and predictability, and once these needs are provided for and the animal is shown how to properly meet those needs, the undesired behavior may cease. So, to illustrate the point of divergence of behavior care and mental health care, consider the example of the cat who is destroying the furniture by clawing. Here, addressing the behavior is essential, but the cat’s mental health does not need help. Conversely, a pet with greatly impaired mental health may show no behaviors that the owner feels need correction. For example, a dog experiencing extreme loneliness may simply ‘suffer in silence’, or another dog with the same emotional distress may exhibit behavior that is an effort to cope with the stress but does not bother the pet’s owner, such as relentless digging in a large yard behind the house. Here, addressing the animal’s mental health is essential, even when there is no ‘behavior problem’ needing correction.

1.3.1 Systemic signs of poor mental health

One challenge in assessing behavior and mental health is that many of the signs may be attributable to mental disorders, physical disorders, or both (see Table 1.1). This crossover in causes means that the first step in the evaluation of these signs should be a veterinary visit with a physical examination and appropriate diagnostic testing to rule out physical health causes. Importantly, however, because it is possible for both a mental health issue and a physical issue to exist at the same time, identifying a physical disorder does not necessary exclude a mental problem. In cases where both co-exist, treating one or the other may or may not create a change in the behavior; it is usually necessary to treat both.

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