Annie didn’t seem herself. She was grumpy and didn’t have much appetite. She seemed lethargic and uninterested in activities she had always enjoyed. Once outgoing, confident and happy, she was now reluctant to do much of anything, preferring to just watch life go by.

Who is Annie? From those vague behaviorial signs, she could be a horse, dog, cat or even a person. It’s not often you’ll be presented with a patient whose owner’s primary complaint is that his animal isn’t happy and may be suffering from mental depression. Nevertheless, decreased appetite and activity along with increased irritability are behavior changes most clients will be concerned about, and which can be associated with a myriad of diseases or illnesses. Some veterinarians use the “ADR” or “ain’t doing right” shorthand for these and other non-specific signs.

As a veterinarian, you’re accustomed to conducting a range of diagnostic procedures when animals present to you with general behavior changes. Before considering a patient’s symptoms the result of mental depression, you know that any medical conditions that could precipitate them must first be eliminated.

If you determine the animal is medically healthy, yet the behavior changes persist, then other possibilities, including depression, should be explored. However, according to Dr. Margie Knoll, a veterinarian and certified veterinary acupuncturist at Airpark Animal Hospital in Westminster, Maryland, there isn’t much information available to general practice veterinarians about the diagnosis and treatment of mental depression in animals.

Defining animal depression

Depression can be defined as a decrease of functional activity, a decreased interest in one’s surroundings and/or a decreased response to external stimuli. In people, depression is typically categorized as situational or chronic (sometimes called endogenous). Situational depression results from a specific event such as the death of a loved one, a divorce, a traumatic experience, or other stressful life events. Chronic depression is not tied to specific events but is more the result of individual, internal risk factors.

Whether animals can have “depressive personalities” is not known. However, research suggests that animals, like people, do have differences in their mental outlooks – similar to the “glass half full or half empty” perspective. In one study, dogs were trained to expect food under a cup in one location but not in another. When the cup was placed midway between the two locations, dogs with separation anxiety were less likely to search the cup for food than dogs without the condition.

In another study, rodents were trained to expect different tones that predicted either an unpleasant noise or a food reward. When a tone intermediate between the two was played, rats raised in a stable environment were more likely to behave as though they expected a reward than those raised in unpredictable conditions.

These differences in expectations likely result from interplays between early experiences and rearing conditions, environmental experiences and learning, and inherent genetic tendencies. Thus, if you suspect an otherwise healthy animal is suffering from a depressed emotional state, the first step is to obtain a behavior history to attempt to identify any contributing events or risk factors.

Causes can be complex

Clear but probably uncommon events that could contribute to a depressed mental state in an animal include traumatic experiences such as surviving a fire, a car or trailer accident, or being caught in a tornado or hurricane. A more common trigger is the loss of another animal or person, through death or separation, to whom the patient was attached. Abuse and neglect may be other factors. It has also been proposed that military dogs serving in combat zones are showing depression-like behavior changes, including a reluctance to engage in tasks for which they were trained. These problems can easily result from classically conditioned fears.

The average pet, however, is more likely to experience a number of insidious conditions that can contribute not only to a depressed mental state but to other behavior problems that compromise his welfare.

Decreased activity, lack of interest, and general passivity are a cluster of behaviors linked to depression. Two risk factors for this behavioral cluster are a lack of control over the environment, and traumatic experiences that also result in a loss of control. It is sad but true that several common animal rearing and training procedures have the potential to create these conditions.

• Excessive crating, too much stall time, or other close confinement means the animal is not able to successfully use his own behaviors to affect any change in his circumstances. Such conditions are often unavoidable at many animal shelters and boarding facilities. However, too many pet dogs are subjected to excessive crating, often more than ten hours a day — either as a routine practice without justification or because unwanted behaviors that precipitated the crating have gone unaddressed. Horses spending too much time in stalls experience similar conditions.

• Secondly, certain “pack leader” or “dominance” theories of pet-people relationships recommend ignoring all the animal’s attempts to interact or solicit play or attention, requiring instead that the owner be the one to initiate all social contact. This removes any way for the animal to ask his owner for what he wants or to have his needs met through his own behaviors.

• Even more likely to cause problems is non-contingent, inescapable, and/or unavoidable punishment. Situations in which an animal’s behavioral response cannot stop or prevent bad things from happening are among the leading causes of the passivity and disengagement often labeled as depression. Outdated training techniques that focus on harsh and abusive physical confrontations and threats that a pet cannot control or predict, produce an animal that is fearful or aggressive. The animal may alternatively adopt a strategy of passivity because the fewer behaviors he shows, the lower the risk of bad things happening.

Behavioral treatment strategies

So what are the practical treatment applications of these findings? Some cases of mental depression may resolve on their own over time. Telling clients to be patient and kind to their animals may allow the depression to resolve. This has been our experience, particularly in cases resulting from the death or loss or another individual. This is borne out by statistics from the human field that show about one third of patients improve without intervention.

Another relatively easy strategy is to create circumstances that allow an animal to receive frequent, high value reinforcement for engaging in simple behaviors, with the goal of getting him moving and interacting again. Simply teaching an animal to use his nose or paw to touch a person’s hand or something held in the hand (a dowel, plastic plate, etc.) creates predictable circumstances, a reinforcement history, and the ability to successfully act on the environment.

Obviously, all harsh training techniques should be stopped. Owners should be instructed to reinforce each and every spontaneous occurrence of active, desirable behaviors with food, play and/or petting and praise.

Physical exercise is known to enhance mood, so simply walking dogs regularly, riding or walking horses, allowing cats safe outdoor time, and engaging pets in play can have a beneficial effect. Close confinement or crating should be minimized.

Certified behavior consultants or experienced certified trainers skilled in the use of both operant and classical counter conditioning and desensitization techniques can teach owners how to implement additional techniques to overcome the fear or anxiety that often contribute to depressive symptoms.

References and further reading

Blood, D.C. and Studdert, V.P., Saunders Comprehensive Veterinary Dictionary, Second Edition, W. B. Saunders, NY, 2000.

Harding E.J., et al, “Animal behavior: Cognitive bias and Affective state”, Nature: 427: 312, 2004.

Hetts, S., Estep, D., and Marder, A.R., “Psychological Well-Being in Animals”, pps. 211-220 in McMillan, F., (Ed.), Mental Health and Well-Being in Animals, Blackwell Publishing, Ames, IA, 2005.

King, L. and Rowan, A. N. Rowan, “The Mental Health of Laboratory Animals”, pps. 259-276 in McMillan, F., (Ed.), Mental Health and Well-Being in Animals, Blackwell Publishing, Ames, IA, 2005.

Mendl, M. et al., “Dogs showing separation related behavior exhibit a ‘pessimistic’ cognitive bias”, Current Biology 20 (19): R839-840, 2010.

Seligman, M.E.P., “Learned Helplessness and Depression in Animals And Men”, pps. 111-126 in Spence, J.T., Carson, R., Thibaut, J. (Eds.), Behavioral Approaches to Therapy, General Learning Press, Morristown, NJ, 1976. Dr. Suzanne Hetts, Ph.D., CAAB and her husband Dr. Daniel Estep, Ph.D., CAAB are award winning speakers and authors, having lectured on four continents to animal parents and professionals. Their company, Animal Behavior Associates, Inc., provides pet behavior education to animal professionals at and animal parents at and


Veterinarian Dr. Janice Huntingford is a graduate of the Ontario Veterinary College, University of Guelph, and certified in animal chiropractic and acupuncture. She received her certification in Veterinary Rehabilitation through the Canine Rehabilitation Institute, and opened Ontario’s first saltwater canine therapy pool and rehabilitation center. She is a Certified TCVM Practitioner, a Certified Veterinary Pain Practitioner, and a board certified specialist, earning a Diploma from the American College of Veterinary Sports Medicine and Rehabilitation. She practices in Essex, Ontario (