Veterinarians must have an understanding of the behavior and development of particular species, the principles of learning, and the clinical signs of fear and anxiety to differentiate normal behavior from abnormal behavior. When presented with a patient with undesirable behavior, the veterinarian must first exclude any medical problems that might be causing or contributing to the behavioral signs.
In addition, although it is common to consider the effects of disease on behavior, stress can cause alterations in behavioral, physiological, and immune responses that can have variable effects on health and behavior with increasing chronicity. Stress leads to alterations in the hypothalamic-pituitary axis and to levels of dopamine, serotonin, norepinephrine, and prolactin. In animals, stress can cause or contribute to feline interstitial cystitis; dermatological, respiratory, and GI disorders; and behavior problems (eg, compulsive disorders, exaggerated fear responses, and psychogenic polydipsia and polyphagia).
Diagnosis of any behavior problem requires the identification of all behavioral and medical clinical signs, a thorough understanding of the patient's history, plus performance of complete physical and neurological examinations, as well as any diagnostic tests indicated to exclude underlying medical conditions that might cause or contribute to the clinical signs (see table Medical Causes of Behavioral Signs).
Medical Causes of Behavioral Signs
| Medical Condition | Behavioral Signs | 
|---|---|
| Illness or disease | Altered personality, lethargy, listlessness, withdrawal, anorexia, decrease in grooming, altered social relationships, altered response to stimuli | 
| Neurological | |
| Central (affecting forebrain, limbic/temporal, and hypothalamic), rapid-eye movement sleep disorders | Altered awareness and response to stimuli, loss of learned behaviors, house soiling, disorientation, confusion, altered activity levels, temporal disorientation, vocalization, change in temperament (fear, anxiety, aggression), altered appetite, altered sleep cycles, interrupted sleep (aggression/waking/activity) | 
| Peripheral (neuropathy) | Self-mutilation, irritability, aggression, circling, hyperesthesia | 
| Focal seizures/temporal lobe seizures | Repetitive behaviors, self-trauma, chomping, staring, altered temperament (eg, intermittent states of fear or aggression), tremors, shaking, interrupted sleep | 
| Sensory dysfunction | Altered response to stimuli, confusion, disorientation, altered sleep cycles, irritability, aggression, vocalization, house soiling | 
| Metabolic/Endocrine | |
| Feline hyperthyroidism | Irritability, aggression, urine marking, increased activity, night waking | 
| Canine hypothyroidism | Lethargy, decreased response to stimuli, irritability, aggression | 
| Panting, night waking, house soiling, irritability, polyphagia, anxiety | |
| House soiling, night waking | |
| Functional ovarian and testicular tumors | Androgen-induced behaviors: males—aggression, roaming, marking, sexual attraction, mounting; females—nesting or possessive aggression of objects | 
| Hepatic encephalopathy; renal encephalopathy | Clinical signs associated with affected organ, anxiety, irritability, aggression, altered sleep, house soiling, mental dullness, decreased activity, restlessness, increased sleep, confusion | 
| Anemia or electrolyte imbalances | Pica | 
| Pain | Altered response to stimuli, decreased activity, restlessness/inability to settle, vocalization, house soiling, aggression, irritability, self-trauma, waking at night | 
| GI | Licking, polyphagia, pica, coprophagia, house soiling (fecal), wind sucking, tongue rolling, unsettled sleep, restlessness | 
| Urogenital | House soiling (urine), polydipsia, waking at night | 
| Dermatological | Psychogenic alopecia (cats), acral lick dermatitis (dogs), nail biting, hyperesthesia, other self-trauma | 
If there is no underlying medical cause for behavioral signs, a comprehensive behavioral history is required to determine the diagnosis, prognosis, and treatment options.
History might be collected in part by having the owner complete a history questionnaire before the visit, especially with respect to data about the home and housing, family, daily schedule, training, husbandry, and background. Interactive questioning and discussion with those responsible for the animal’s care, housing, and training are required to further evaluate the progress and development of the problem from its inception to the present. Having the owners bring video clips of the behaviors can help provide insight for the diagnosis, prognosis, and management or improvement of the problem.
For each behavior problem, the antecedent, behavior, and consequence (ABC model used in applied behavior analysis therapy) should be considered. The antecedent is what precedes the undesirable behavior; the behavior is the description of the problem that occurs after the antecedent; and the consequence is what happens immediately after the behavior. With maturity and learning, the animal can be taught to respond differently to a stimulus; thus, the events initiating a problem behavior may be just as important to evaluate as more recent events that perpetuate it.
The history should include the following information:
- the animal's sex, breed, and age 
- description of undesirable behavior (in the ABC) 
- age at onset 
- duration 
- frequency (hourly, daily, weekly, monthly) 
- intensity of bouts 
- duration of bouts 
- any changes in pattern (eg, change in frequency, intensity, or duration of bouts) 
- treatment measures tried and the responses 
- any activities that stop the behavior (eg, animal collapses) 
- 24-hour schedule of animal and owner, as well as any day-to-day variability 
- environment and housing 
- animal’s familial history (eg, people and other animals in the household or property) 
- genetic behavioral influences (eg, pedigree's behavior, genetic relatives' behavior), if known 
- anything else the owner thinks is relevant 
With production animals, questions should be framed within the context of the problem so that housing, management, group or herd behavior, production, and perhaps reproduction are addressed.
Additional information about the pet’s personality, relationship with the owner, and response to stimuli, as well as the owner's response, might be gained during the visit by observing the pet and its interactions with the owners.
Provoking the pet to perform the undesirable behavior is generally contraindicated because any further repetition of the problem is ill-advised for the pet and might lead to further undesirable learning. A controlled interactive assessment might include how the patient responds to other animals, people, sounds, a childlike doll, or handling, including physical examination, petting, or the application of products such as a head halter, muzzle, or body harness. The pet’s response to commands can be assessed during the visit, as well as the types of treats or toys most likely to positively affect the pet.
