Pharmacologic treatment of fear and anxiety in canines

Pharmacologic Treatment of Fear and Anxiety in the Canine

Anyone who has ever owned a dog that was scared of certain events, objects or people can readily testify to how profound the fear can be in various breeds of canines. In fact, more than half of Americans own dogs today, and the number continues to increase. The symptoms of such fear and anxiety can range the entire spectrum from mild to life-threatening conditions, and pet owners, military and police dog handlers, veterinarians and others concerned about the welfare of their animals will need all of the help they can get when confronted with these types of conditions in their household dogs and other canines. To this end, this paper provides an overview of the problem including causes and symptoms of fear and anxiety in canines, followed by a critical analysis of the current and peer-reviewed literature concerning the pharmacologic treatment of these disorders today. A summary of the research and salient findings are provided in the conclusion.

Review and Discussion

Background and Overview.

Mankind has always wanted to communicate with animals, and to some extent, this communication is possible with many species such as the great apes, dolphins and common households dogs and cats. Unfortunately, this level of communication does not typically include the ability to discern specific psychological conditions that are found among humans but may not have an exact counterpart in the rest of the animal kingdom. In this regard, Plutchik (2001) reports that, "By now we have all heard authors of best-selling books describe jealousy, love, anxiety and fear in dogs, cats, chimpanzees, baboons, elephants and lions. The popular appeal of such explanations may lie in their ability to touch a deep-seated sense of the connectedness of all living things" (p. 344). While a number of clinicians have cautioned that there are some serious implications involved in such anthropomorphism, the growing body of scientific evidence suggests that this attitude is an obsolete prejudice. In fact, according Donald Griffin, one of the founders of the field of animal cognition and a zoologist at Rockefeller University, the "charge of anthropomorphism is a conceited claim that only our species is capable of even the simplest conscious thinking. But there is danger in oversimplifying: A sophisticated understanding is needed to inform clinical practice" (cited in Plutchik, 2001, p. 344).

From a clinical perspective, Sher and Trull (1996) note that there are a number of naturally occurring behavior disorders that are typically treated in veterinary practices that may have relevance to a number of human conditions; these conditions include, but are not limited to, stereotypic disorders (e.g. excessive grooming), aggression, mood disorders, anxiety disorders, eating disorders, hyperactivity, and sleep disorders. These authors add that researchers generally use a wide variety of experimental manipulations to induce specific signs and symptoms or more complex syndromes in animals that have some similarity to human psychopathologic phenomena with the majority of these behavior disorders in animals (Sher & Trull, 1996). Despite these constraints, though, researchers continue to use animal models to study the mechanisms that are involved in several psychiatric disorders and to investigate the relationship between conditions such as alcoholism and co-occurring disorders that have shed some insight into the etiology of these processes in the canine as well as humans (Hitzemann, 2000). An old adage advises that the dog is "man's best friend," and there does in fact appear to be a special bond that exists between many dogs (Swabe, 1999). According to this author, "Archaeological findings suggest that Canis familiaris was probably the first animal species to undergo domestication" (Swabe, 1999, p. 33). In fact, the special relationship between mankind and canines that has historically existed has resulted in the species that exists today (Swabe, 1999). Indeed, a growing body of medical evidence indicates that dogs can reduce stress among humans and it is little wonder, then, that many dog owners hold their pets in high esteem (Jalongo, 2005), some to the extent that they have sought to have their dogs cloned (Fiester, 2005). Furthermore, the number of people who own dogs in the United States today is greater than ever and continues to increase (Becker, Chew, Correa, Hoepner, Jusino, Kinney, Miller & Perzanowski, 2003; Boone & Tyler, 2001). According to a survey by the Pet Food Institute, more than 50% of all households in the United States have some kind of pet, and the number is rising: "By far the most popular pets are dogs and cats. The number of dogs owned by Americans increased 13% between 1982 and 1990" (Williams, 1991, p. 24). The importance of identifying typical symptoms and sources of fear and anxiety in canines, then, has assumed a new level of importance today for the average dog owner, and these issues are discussed further below.

Causes and Symptoms of Fear and Anxiety in Canines.

Although researchers continue to refine their understanding of fear and anxiety in canines, much has been learned about how these physiological and psychological processes operate in them. For example, researchers recognize that all types of organisms must determine, based on limited information, whether there is adequate food, potential mates or danger in their environment; depending on the type of prediction made about these issues, the organism then makes a decision to escape, to attack, to eat or to mate (Plutchik, 2001. In this regard, Singer (1990) cites numerous neurologists, animal behaviorists, and "three separate expert government committees on matters related to animals" to support the claim that animals perceive pain, as well as fear, anxiety, and stress.

According to Ridley (1999), dogs that are household pets are at particular risk of developing various fears and anxieties as the result of their owners' negative behaviors and moods. "Black moods and tantrums from humans are frightening and often result in pets becoming noisy and destructive," he advises. "They develop canine anxiety and are unable to cope with the mayhem that is erupting around them. In extreme cases, domestic disruption can cause confusion and terror which trigger symptoms in a dog that are exactly the same as the ones they will experience when they are about to die" (p. 38). Furthermore, empirical observations from this author confirm that dogs will in some cases mimic the same types of behaviors found in the wild that are indicative of fears and anxieties, even to the extreme of losing the will to live (or at least continue to live with the same owners). In this regard, Ridley reports that, "I have seen dogs go to the bottom of the garden, or stay close to walls - their heads and tails hanging low - which normally is an instinctive reaction to impending death. In the wild dogs leave their packs and go away to die" (p. 38).

Finally, while cats are also highly sensitive to these types of human behaviors, cats tend to cope with these issues as individuals but dogs have an intuitive and overpowering sense of their pack instinct: "A dog's pack is the family unit. A fracas among humans, or one member leaving will disturb the animal. Remember, our pets are unable to understand what is going on" (Ridley, 1999, p. 39). When dogs suddenly turn destructive and aggressive, the outcomes can be distressing and even dangerous for the owners. For instance, citing the case of a Doberman named Rex that turned against its mistress after her husband left home, Ridley reports that the woman was no longer able to control the large dog within a week Rex bit her so badly she required stitches in her arm and leg. The author's conclusion: "Rex regarded the woman's husband as the leader of the pack and was thrown into confusion when he left. I persuaded the lady to let Rex live with her estranged husband and Rex immediately returned to his immaculate behaviour" (Ridley, 1999, p. 39).

Likewise, another divorcing couple owned a pair of Jack Russell terriers and decided to keep one dog each; however, both dogs immediately became uncontrollable. According to Ridley's assessment, "These dogs had been inseparable for three years and couldn't bear to be parted. The couple agreed to re-unite them and the problems ceased" (Ridley, 1999, p. 39). Finally, the author cites the case of Max, a small Maltese who had been overindulged by his mistress (even allowing him to sleep on her bed). "When her lover moved in to the bedroom, Max became vicious and was threatening the relationship. Sometimes arguments over a pet can lead to divorce. I advised this man to make friends with Max and gently ease him out of the bedroom. He did his best, but sadly it came too late to save the relationship. The lady had raised Max's status to the point where he was the boss" (Ridley, 1999, p. 39).

In this regard, learned helplessness and the related phenotypes of behavioral despair and chronic unpredictable stress have been used by researchers to model some aspects of depression. For instance, Martin Seligman originally developed the learned helplessness model by exposing dogs to shocks from which they could not escape; over time, the dogs resigned themselves to their fate and made no effort to escape the shocks (i.e., they became helpless). Furthermore, other behaviors of the dogs were adversely affected (e.g., the dogs appeared apathetic and had poor appetites) (Hitzemann, 2000). In his essay, "Animal Models of Psychiatric Disorders and Their Relevance to Alcoholism," Hitzemann (2000) reports that, "Both fear and anxiety are alerting signals that warn the individual against impending danger and enable the individual to take defensive measures. For animals, the distinctions between fear and anxiety are vague" (p. 149). The distinctions between fear and anxiety are clearly irrelevant for humans who encounter such stressed animals, though.

According to Hodge and Stull (2000), dog bites cause an average of 17 human deaths, 6,000 hospitalizations, and 330,000 emergency room visits every year in the Untied States and a like number of people probably do not seek treatment or report the incident, but may nevertheless experience psychological trauma, anxiety, and missed work or school. Furthermore, dog bites continue to be a potential source of rabies infection that requires postexposure prophylaxis (Chang, Cohen, Hennon, LaPorte, & McMahon, 1997, cited in Hodge & Stull, 2000, p. 17). Dog bites, of course, are just one of a wide range of behavioral disorders that can result from fear and anxiety in dogs (Duke & Swain, 2001). The Merck Veterinary Manual provides the following list of fear- and anxiety-related behavioral disorders among dogs:

Abnormal ingestive behavior. This condition is characterized by the following symptoms: consistent ingestion of abnormal amounts or types of food or nonfood material in a manner or frequency not consistent with previous behavior. The following condition is sufficient for assignment of this diagnosis: incessant consumption of food or nonfood material, or incessant avoidance of food, in a manner that interferes with normal social functioning; abnormal ingestive behavior includes (a) pica (consistent ingestion of nonfood material), (b) coprophagia (ingestion of feces that is neither accidental nor incidental), - polyphagia, aerophagia, psychogenic water drinking (consumption of water in excess of that necessary to meet daily fluid balance needs or to thermoregulate or lubricate food for ingestion), (d) anorexia, and (e) gorging. In their extreme, pica, aerophagia, and coprophagia may be signs of obsessive-compulsive disorders;

Attention-seeking behavior. This diagnosis requires that the dog must use vocal or physical behaviors to obtain passive or active attention from people when the people are doing something not directly involving the dog. The following condition is sufficient for this diagnosis: whenever a person is not directly engaged in passive or active interaction with the animal, the animal uses active or passive behaviors to direct some of the person's attentions to itself and will interrupt human activity to do so;

Cognitive dysfunction or senility. This condition has the following necessary and sufficient condition: change in interactive, elimination, or navigational behaviors attendant with aging that are explicitly not due to primary failure of any organ system; however, many dogs with extensive plaque formation experience no diminishment in their cognitive function; while there are a number of medications available for the treatment of this condition in humans, just one drug (selegiline) is currently approved for canine cognitive dysfunction in the United States. Besides pharmacologic interventions for cognitive dysfunction in canines (which will likely require lifelong treatment), other interventions have been found effective in reducing these symptoms in older dogs, including cognitive enrichment and a prescription diet;

Compulsive licking. This disorder requires the following necessary condition: licking in excess of that required for standard grooming or exploration with the following condition being sufficient for diagnosis: licking in excess of that required for grooming or exploration that represents a change in the animal's typical behavior and interferes with other activities or functions (eg, eating, drinking, playing, interacting with people) and cannot easily be interrupted. In addition, Merck notes that fearful behavior or fear that the necessary and sufficient condition for this disorder includes: any type of behavior that takes place at the same time accompanied by relevant behavioral and physiologic signs (e.g., withdrawal, passive, and avoidance behaviors associated with the sympathetic nervous system), together with the absence of any aggression. Further, fear and anxiety have overlapping indicators; some nonspecific signs include avoidance, shaking, and trembling, which can be characteristic of both disorders;

Generalized anxiety. This disorder has the following necessary conditions: (a) consistent display of autonomic hyperreactivity, (b) increased motor activity, and - increased vigilance and scanning that interferes with a normal range of social interaction; however, the authors caution that this disorder should be regarded as a diagnosis of last resort, and all of the signs should be concomitantly present under conditions in which any of these signs would have subsided in a normal or asymptomatic animal.

Hyperactivity. This disorder has the following necessary condition: motor activity in excess of that warranted by the animal's age and stimulation level that occurs in a consistent, often stereotypical, manner and does not respond to correction, redirection, or restraint; like their hyperactive human counterparts who are treated with the stimulant Ritalin, dogs that are suffering from this disorder tend to respond to treatment with amphetamine or methylphenidate with a paradoxical decrease in motor activity. According to Merck, the majority of dogs that owners consider to be hyperactive (a diagnosis that does not depend on the dog's exercise level compared with its needs) are actually overactive (a diagnosis that does depend on the dog's exercise level compared with its needs. Clinical hyperactivity in dogs remains a specific diagnosis for which specific behavioral signs have not been clearly identified and is regarded as a rare condition.

Inappropriate play behavior. This disorder has the following necessary and sufficient condition: play behaviors such as play bows, yips, or shoulder blocks;

Neophobia. This disorder has the following necessary and sufficient condition: consistent, sustained, sudden, profound nongraded response to unfamiliar objects and circumstances manifest as intense active avoidance, escape, or anxiety behaviors associated with the activities of the sympathetic nervous system; in this condition, canine behaviors include immobility or extremely high activity, together with decreased sensitivity to pain or social stimuli; and, repeated exposure results in an invariant pattern of response;

Noise phobia. Perhaps one of the most common fear- and anxiety-related disorders among canines, this is characterized by the following necessary and sufficient condition: sudden and profound, nongraded, extreme response to noise manifest as intense active avoidance, escape, or anxiety behaviors associated with the activities of the sympathetic nervous system;

Obsessive-compulsive disorders. This disorder has the following necessary condition: repetitive, stereotypic motor, locomotory, grooming, ingestive, or hallucinogenic behaviors that occur out-of-context to their normal occurrence, or in a frequency or duration in excess of that required to accomplish the ostensible goal;

Overactivity. This canine disorder has the following necessary condition: motor activity that is in excess of that exhibited when the animal experiences a regular exercise and interaction schedule; however, the diagnosis of overactivity depends on the context and must take into account the age, breed, and social and physical environment of the dog, as well as the owner's perception;

Pseudocyesis (false pregnancy). This disorder has the following necessary condition required for this diagnosis: maternal behavior exhibited in the absence of pregnancy;

Roaming. This disorder is characterized by the following necessary and sufficient condition: locomotory activity involving extended absences and greater distances than those needed for the animal to relieve itself;

Separation anxiety. This disorder has the following necessary condition required for assignment of this diagnosis: physical or behavioral signs of distress exhibited by the animal only in the absence of or lack of access to the owner (Other Canine Behavioral Problems, 2006).

On a final note, the authors emphasize that the exact extent to which animals with separation anxiety tend to experience other types of fear- or anxiety-related behaviors remains unknown. According to Merck (2006), "There is now a well-established comorbid association between separation anxiety and noise and thunderstorm phobias, so any dog exhibiting signs of one condition should be screened for the others. Both sets of conditions should be treated, although treatment schedules and drugs of choice will differ (e.g., noise/thunderstorm phobias require that benzodiazepines, preferably alprazolam, be given as needed, and separation anxiety should be treated with tricyclic antidepressants or selective serotonin reuptake inhibitors daily" (Other Canine Behavioral Problems, 2006). p. 9). The studies to date have also found that the attentiveness of the owners is not a factor in this condition, but there is a population of dogs that experience separation anxiety that are also hyperattached and must remain in sight or touch of their family at all times; this extreme variant requires intensive treatment, including extensive behavior modification to teach the dog (and possibly the client) to be less dependent (Other Canine Behavioral Problems, 2006).

Pharmacologic Treatment of Fear and Anxiety in Canines.

Depending on the species of canid involved (for example, zoological veterinarians are required to treat a wide range of species), pharmacologic treatment of fear and anxiety can be accomplished using various medications, which are discussed further below. According to the Merck Veterinary Manual (2006), the majority of behavior modification interventions with dogs focus on desensitization and counterconditioning. "This is most important in the early treatment of fears, phobias, and anxieties," the authors advise. "The earlier the treatment is started, the better the prognosis. Early intervention with antianxiety medication may be preferred for most anxieties, OCD, and phobias. Noise phobias often respond to diazepam, chlorazepate, or alprazolam (the drug of choice for many of these patients) if administered 1-2 hr before the onset of the expected stimulus" (p. 4). These treatments can be repeated just prior to at the onset of the fear- or anxiety-producing event and every 4-6 hours thereafter as required. Longterm or maintenance treatment for comorbid anxiety, though, should be implemented through the use of a specific serotonin reuptake inhibitor (e.g., fluoxetine, sertraline) or a more recent tricyclic antidepressant such as clomipramine (Other canine behavioral problems, 2006). The authors add that recurrence rates are high, particularly if the pharmacologic intervention is stopped prematurely: "Pharmacologic treatment will need to be given for at least 4-6 months and may be lifelong," they advise. "Because these medications have relatively few side effects, longterm treatment is not problematic if the client complies with recommendations for routine evaluation (eg, physical exam, urinalysis, CBC, serum biochemistry panel, and possibly ECG)" (Other canine behavioral problems, 2006, p. 5).