Diagnosis and management of compulsive disorders in dogs and cats

Diagnosis and Management of Compulsive Disorders in Dogs and Cats Andrew U. Luescher, DVM, PhD

R

epetitive or sustained apparently abnormal behaviors performed out of context have been described in various species of farm animals and zoo animals, especially in horses. In horses, these behaviors have often erroneously been termed stable vices and include cribbing, weaving, stall walking, stargazing, and aggression to self. There is a vast literature on this behavioral abnormality in these species.1 These abnormal behaviors have always been considered to develop from confinement-induced conflict behaviors and have been linked to specific husbandry practices.2 The term conflict usually refers to motivational conflict (ie, the conflict resulting from two opposing similarly strong motivations (eg, approach and withdrawal). Frustration refers to the situation in which an animal is motivated to perform a behavior but is prevented from doing so. Various forms of conflict behaviors are caused by frustration or conflict and have been studied in a great variety of species.3 They are mostly derived from normal behaviors relating to different motivational systems. With repeated or prolonged conflict or frustration, these behaviors become “emancipated” from their original context; become exaggerated, repetitive, or sustained; and are triggered in a variety of situations by a progressively lower level of arousal.4 In companion animals, behaviors such as “fly snapping,” tail chasing, or wool sucking were more commonly considered to be symptomatic for seizure disorders, and treatment was usually unsuccessfully attempted with seizure-controlling drugs. In 1991, we proposed that these abnormal behaviors in companion animals were homologous to the stereotypic behavior of livestock and zoo animals.5 Around the same time, researchers at the National Institutes of Health (NIH) recognized that these behaviors shared similarities with human obsessive compulsive disorder (OCD).6 Since that time, when exhibited by companion animals, these abnormalities are usually referred to as OCD5,7 or compulsive disorder (CD).8 Obsessive compulsive behaviors Department of Veterinary Clinical Sciences, Purdue University School of Veterinary Medicine, 1248 Lynn Hall, West Lafayette, IN 47907-1248, USA. Address reprint requests to Andrew U. Luescher, DVM, PhD, Department of Veterinary Clinical Sciences, Purdue University School of Veterinary Medicine, 1248 Lynn Hall, West Lafayette, IN 47907-1248. E-mail: [email protected] Reprinted with permission from Veterinary Clinics of North America: Small Animal Practice 33(2):253-267, 2003. © 2003 Elsevier, Inc.

1096-2867/04/$-see front matter © 2004 Elsevier Inc. All rights reserved. doi:10.1053/j.ctsap.2004.10.005

in people include repetitive behaviors, such as hand washing, rituals, checking, arranging/ordering, counting and hoarding, and are accompanied by intrusive thoughts, such as concern of contamination; concern for symmetry; fear of harm; aggressive, religious, or sexual thoughts; or pathologic doubt. Interestingly, the intrusive thoughts (obsessions) and the associated behaviors (compulsions) do not necessarily correspond. For instance, checking can be accompanied by aggressive, sexual, religious, or somatic obsessions.9 Compulsive behaviors are carried out to reduce discomfort or to prevent a dreaded event.10 The extent of the similarities between the human and canine conditions is not yet known. One similarity is that, overall, the behaviors in companion animals are amenable to the same pharmacologic treatment as are obsessions and compulsions in people. Another similarity is the type and repetitiveness of behavior displayed (actually, the first connection between the canine and human disorders was made because dogs with acral lick dermatitis appeared similar to people washing their hands repetitively and excessively). There are differences between the human and canine conditions. Obsessions in animals are not amenable to direct study, and because obsessive thoughts and the compulsive behavior do not necessarily correspond even in people, it is difficult to draw conclusions regarding obsessions from the observed behavior. In human beings, the intrusive thoughts are experienced as being disturbing. Most patients try to resist them and are ashamed and disgusted. The behavior is considered senseless by the patient. All this adds to stress. Also, obsession compulsion disorder (OCD) patients tend to have an inflated sense of responsibility and great need for reassurance. I find it hard to see these in, for example, a tail-chasing dog. Furthermore, OCD implies a cognitive component.11 In what is grouped here as canine CD, the cognitive component and the cognitive control over the performance of the behavior may vary considerably (see section on homogeneity of CD). A lot more work is needed to validate the diagnosis of CD or OCD.12 As a working definition of CD, Hewson and Luescher8 proposed the following: Behaviors that are usually brought on by conflict, but that are subsequently shown outside of the original context. The behaviors might share a similar pathophysiology (e.g. changes in serotonin, dopamine and beta233

A.U. Luescher

234

Figure 1 This English Bull Terrier fixated on any object on the floor. This picture illustrates the dog’s reaction to the water bowl after approaching it to take a drink. The dog had to be given water from a bottle to prevent dehydration.

Figure 3 This Great Dane would “hide” under a curtain and freeze.

endorphin systems). Compulsive behaviors seem abnormal because they are displayed out of context and are often repetitive, exaggerated or sustained. ●

Presenting Signs of Compulsive Disorder The behaviors performed by dogs and cats with CD could be categorized as locomotory, oral, aggressive, vocalization, and hallucinatory behaviors (Figs. 1-6). ● ●

●

In dogs, locomotory behaviors include circling, tail chasing, pacing, jumping in place, chasing light reflections, and freezing; in cats, locomotory behaviors include freezing, sudden agitation and skin rippling, ducking, and circling. Oral behaviors manifest in dogs as leg or foot chewing, self-licking, air or nose licking, flank sucking,

Figure 2 A hind-end checking Miniature Schnauzer.

●

scratching, chewing or licking of objects, polyphagia, polydipsia, pica, and snapping in the air (fly snapping); in cats, oral behaviors manifest as overgrooming (“psychogenic dermatitis”), chewing legs or feet, chewing or licking objects, wool sucking or eating, and pica. Compulsive behaviors related to aggression in dogs include self-directed aggression, such as growling or biting the rear end, rear legs, or tail; attacking the food bowl or other inanimate objects; and possibly unpredictable aggression to people; in cats, compulsive behaviors include self-directed aggression, especially attacking the tail. Vocalization may be compulsive rhythmic barking or whining and persistent meowing or howling. Hallucinatory behaviors may be staring at shadows, chasing light reflections, and startling. Dogs that wake up suddenly without any discernible trigger and jump or are aggressive may suffer from hallucinatory CD. Cats that avoid imaginary objects, stare at shadows, or startle without obvious cause may fall into the same category.

Figure 4 Fixation on an object in a Rottweiler.

Compulsive disorder in dogs and cats

235 such as dermatologic disease or endocrine imbalance, may contribute to CD as well.

Conditioning Most owners pay attention to their pets when they perform a compulsive behavior. Therefore, most cases of CD are aggravated by inadvertent conditioning. Performance of the behavior only in the owner’s presence is suggestive of a purely conditioned behavior.

Pathophysiology of Compulsive Disorder

Figure 5 Foot chewing in a Dalmatian.

Causes of Compulsive Disorder Stress In agreement with the theory of stereotypic behavior in farm animals, we consider compulsive behaviors to be conflict behaviors caused by environmentally induced conflict, frustration, or stress. Therefore, any environmental factor resulting in frustration (eg, no exercise off property), conflict (eg, inconsistent interaction), or stress (eg, the presence of other stressful behavioral problems, such as dominance conflict with another dog, separation anxiety, or disease) may contribute to the CD.

Genotype A genetic predisposition is probably present in any case of CD. Individuals may be genetically susceptible to development of a compulsive behavior, or the genotype may determine which, if any, compulsive behavior an animal develops. Apparent breed predispositions include flank sucking in Dobermans; spinning or freezing with the head under or between objects, such as clothes, in Bull Terriers; tail chasing in German Shepherds and Australian Cattle Dogs13; and checking the hind end in Miniature Schnauzers. Furthermore, large-breed dogs seem to be more likely than small-breed dogs to develop lick granulomas. In cats, it seems that Siamese and Burmese breeds are particularly prone to develop wool sucking.5 Temperament traits, such as genetic fearfulness, are likely to contribute to the development of a CD as well.

The pathophysiology of CD is not well understood. Most evidence stems from drug effects on the performance of compulsive behavior. Large doses of dopaminergic drugs, such as amphetamine or apomorphine, are effective in inducing stereotyped behavior in animals, whereas the dopamine antagonist haloperidol results in suppression of spontaneously occurring stereotyped behavior.14 The role that ␤-endorphins play in the development of compulsive behavior is not known, but it has been suggested that they play a significant role only in the initial stages of stereotypy development.14 The ␤-endorphin antagonists can be effective in suppressing compulsive behaviors, but their application in clinical cases is not practical. Similar to the treatment of human OCD, drugs inhibiting serotonin reuptake have been found to be effective in the treatment of CD in dogs.6,15 The effectiveness of such drugs implies that serotonin is involved in animal CD. Direct evidence of serotonin involvement has also been presented.16

Development of Compulsive Behavior If compulsive behaviors in dogs are homologous to stereotypic behaviors in farm animals, one would expect them to be shown first in specific conflict situations (acute or normal conflict behavior) and, with prolonged or repeated conflict, to become generalized to other contexts in which the animal

Medical Problems In some cases, a dog may start to lick a lesion or sutures but then also start to lick other parts of the body. Persistent licking may cause lick granulomas at sites unrelated to the original lesion. This suggests that the stress associated with physical lesions or irritations, such as those caused by allergy, can contribute to the development of CD in an already susceptible animal and that the irritation can initially direct the compulsive behavior toward a particular body site. Any other disease that increases stress and/or irritability,

Figure 6 This Jack Russell Terrier paced the room, always staring at the ceiling. It would walk into objects that were in its way.

A.U. Luescher

236 experiences a high level of arousal. As the number of eliciting contexts increases, the threshold of arousal needed to elicit the compulsive behavior decreases and the compulsive behavior becomes more and more frequent. The compulsive behavior can interfere with normal function and affect the human-animal bond.17 This is indeed the pattern for some (mostly locomotory) compulsive behaviors. Interestingly, in a clinical trial involving 51 dogs with CD, it was found that this process was reversed during treatment. When the severity of CD was rated as improving, the number of contexts in which the behavior was displayed also decreased.15

Homogeneity of Compulsive Disorder Aside from the fact that several of the behaviors described in this article may be found to have other possibly medical or neurologic reasons in the future, there is some evidence that CD is not a homogeneous condition and that there may be different classes of compulsive behavior.

Development The categories of locomotory and oral compulsive behaviors seem to differ. In general, locomotory compulsive behaviors follow the above described development pattern, starting in one context and gradually generalizing to other contexts in which the animal is agitated. Oral self-directed behaviors, however, seem to be displayed suddenly without identifiable initial conflict and are performed at a constant rate in contexts with little outside stimulation, (ie, when the animal seems quiet [although its arousal level may be high]). Owners often describe that it appears as if the dog had to perform the oral compulsive behavior so as to be able to settle down. Neurophysiologic studies also seem to justify this categorization. It was suggested that oral stereotypic behaviors may involve the mesolimbic dopaminergic system, whereas locomotory stereotypic behaviors may involve activation of the nigrostriatal dopaminergic system.18

Level of Cognition Involved Some behaviors, such as fly snapping or spinning, seem to involve little cognition and seem more akin to tic disorders in human beings. Other CDs, however, seem to involve a high level of cognition. For example, Miniature Schnauzers that are hind-end checkers are not simply looking at their hind end in a repetitive constant fashion. First, they may turn either way. More importantly, they may get up and check the floor where they have been sitting and perhaps even scratch it. This implies that they actually perceive that there is something wrong. Dogs that chase light reflections may wait in the morning in the appropriate location where they know the rising sun produces the first light reflections. Dogs that are fixated on a particular object may look for that object when it is removed.

Ease of Distraction Some patients can easily be distracted with an innocuous noise, such as clicking of the tongue. An example was a 2-year-old German Shepherd that chased its tail. In other cases, the behavior can only be interrupted by physically

interfering with the behavior (eg, by pulling on a leash attached to a head halter), as was the case with a Border Collie that chewed its front foot. In some cases, even that is not possible. A Jack Russell Terrier would attack itself ferociously in response to minute triggers. No noise or visual distraction worked, and attempts to interfere physically increased the intensity of the behavior even further. It is unknown if these behaviors represent different behavioral pathologic characteristics or if they simply differ in severity. Up to this point, a clinical relevance for these distinctions has not been established. In a clinical trial investigating the efficacy of clomipramine in the treatment of CD, there was no difference in response to drug treatment between locomotory and oral compulsive behaviors.15 We also suggest the same behavioral treatment for all compulsive behaviors.

Clinical Approach to Compulsive Disorder Diagnosis A diagnosis of CD is primarily based on a detailed history and on ruling out other possible causes for the observed behavior. The history includes information on the life history (ie, source, age obtained) and management (ie, exercise, confinement, training, feeding, owner-dog interaction) of the animal, the disposition or temperament of the animal, and the compulsive behavior itself. General information on the problem includes the contexts in which the behavior occurs (triggers of the behavior), a description of the behavior, and the events that follow the behavior. The ease or difficulty with which the animal can be distracted should be noted as well. Age of the dog at the onset of the problem and any correlated change as well as previous attempts by the owner to treat the problem are recorded. One aspect of the history that is particularly important for the diagnosis is the development of the problem. This is assessed by comparison of the contexts in which the behavior was shown initially and the contexts in which it is shown now and the change in the intensity of the inciting stimulus needed to trigger the behavior. To exclude other possible causes for the behavior, a minimal medical database consisting of a physical examination, including a basic neurologic examination, complete blood cell count (CBC), chemistry profile, and urinalysis should be obtained. The basic neurologic examination19 includes observation of the animal (ie, movement, balance); symmetry of face and eye position; and testing of the menace reflex, the eye blink reflex, vestibular eye movement, and the pupillary reflex. Sensation on the nose and lower jaw and jaw tone are assessed. Symmetry of the larynx, pharynx, and tongue is observed, and the gag reflex is tested. The masseter, trapezius, and brachiocephalicus muscles are palpated to assess atrophy, and the spine is palpated. Hopping and proprioceptive positioning are tested. Hearing can be tested by making a noise behind the dog and watching for a reaction. This basic neurologic examination should determine if neurologic problems are present or not. If the results are normal, further neurologic testing is not warranted. In some cases, further tests, such as electroencephalography (EEG), neurologic imaging and spinal tap, vision and hearing tests, endocrinologic

Compulsive disorder in dogs and cats assays, and dermatologic diagnostics, may be indicated. In cases with suspected psychogenic polydipsia, a modified water deprivation test may need to be performed. Compulsive behaviors are always displayed outside their natural context, usually in several different contexts, and/or are excessive. They are often directed toward unusual target objects and are frequently repetitive or sustained. The animal is in full consciousness while performing the behavior and aware of its surroundings (although it may not respond to any stimuli in the environment in some cases and may even run into furniture, for example). The behavior can usually be interrupted, and the animal does not exhibit a postictal phase characteristic of seizures. Performance of the behavior is not dependent on the owner’s presence (to exclude attention getting behaviors). Locomotory compulsive behavior and fly snapping are typically initially shown in a specific conflict situation and, later, in an increasing number of situations in which the animal is excited. Self-directed oral compulsive behaviors are likely to be shown in situations with little external stimulation.

Differential Diagnosis The differential diagnosis has to consider various behavioral, neurologic, dermatologic, and other medical conditions.

Behavior Whenever an animal is in a situation of frustration or motivational conflict, it is normal for it to demonstrate (acute) conflict behavior. In contrast to compulsive behavior, conflict behavior is shown only in conflict situations and not when an animal reaches a threshold of arousal for other reasons, such as anticipation of being fed. In contrast to selfdirected oral compulsive behavior, acute conflict behavior is not shown in situations in which there is no outside stimulus inducing a conflict. A specific conflict behavior could have been shown once in an acute conflict and then may have become conditioned by the owner paying attention to the animal. Such behavior is only shown in the owner’s presence. We therefore always ask in the history if the problem is also performed when the animal is alone (eg, outside in the yard or in another room). We also ask what attention-getting behavior the dog is normally showing.

Neurology Seizures need to be differentiated from CD. Circling Bull Terriers were reported to have an abnormal EEG indicative of seizure activity.20 Seizures rarely look like CD, however. Animals performing compulsive behaviors are aware of their surroundings, can usually be distracted (although sometimes with difficulty) from performing their behavior, and, most importantly, do not show a postictal phase. As opposed to seizures, animals perform the compulsive behavior usually when alert and interacting with their environment. Also, seizures do not follow the pathogenesis typical for CD. Neurologic disorders, such as forebrain and brain stem lesions, may cause an animal to walk aimlessly in large circles. Circling in tighter circles with a head tilt indicates involvement of the vestibular system.19 In these cases, circling is related to a balance deficit. Circling has also been attributed

237 to lumbosacral stenosis or cauda equina syndrome. Hydrocephalus has been suggested as a cause of circling in Bull Terriers.21 Sensory neuropathies can induce chewing on the feet among other signs. Pain sensation in the distal extremities is reduced. The condition can be hereditary and is then usually apparent in young animals.19 Tail dock neuroma may draw a dog’s attention to its hind end. The author is not aware of any case, however, in which tail-dock neuroma was a proven cause for circling behavior or aggression to the tail.

Dermatology Any dermatologic lesion or skin gland disease resulting in itching or pain can cause licking. Dermatologic conditions that need to be considered include staphylococcal furunculosis, dermatophytosis, mycotic or mycobacterial granuloma, allergies, and endocrinologic imbalance. Licking, in turn, can worsen many dermatologic lesions, resulting in an itchscratch or itch-lick cycle. Licking may persist even long after the initiation dermatologic cause has been removed.22 Dermatologic conditions also likely impose some stress on the animal, increasing the likelihood of that animal developing a CD. Thus, there is a mutual influence between the dermatologic and behavioral condition, resulting in a vicious cycle. Dermatologic lesions, such as preexisting wounds or pressure point granulomas, can also direct compulsive licking toward a particular area.

Treatment Because a CD derives from conflict behavior, an attempt should be made to identify and remove the cause of conflict, frustration, and stress. In cases where the cause of stress cannot be removed, it may be possible to desensitize the animal to the stressful situation. Lack of predictability and control over the environment is an important stress-inducing factor and may arise from inconsistent owner-animal interaction, lack of training to commands, and thus inconsistent use of commands. The inappropriate use of punishment, an inconsistent routine, and frustration of motivations, such as the motivation for social interaction, are additional contributing factors. Casual interaction should therefore be avoided and replaced with highly structured interactions in a commandresponse-reward format. Formal obedience sessions allow for such consistent interaction with dogs and establish a habit of using consistent commands in everyday situations. In cats, we recommend regular quality time at a time of day when it can always be provided. The owners are advised to play with the cat with toys or to clicker-train them to do tricks, such as retrieving a ball. Owners frequently apply punishment (eg, scolding). Because it is practically impossible to apply owner-related punishment correctly (ie, with correct timing, at the right intensity, and every time the objectionable behavior is shown), such punishment becomes unpredictable and thus stressful. It should therefore not ever be used in affected animals. An acceptable alternative to punishment is response substitution. If the animal engages in an inappropriate behavior, it is

A.U. Luescher

238 Table 1 Pharmacologic Treatment of Compulsive Disorder Drug

Dose rate

Side effects

Contraindication Liver disease, history of seizures, cardiovascular problems, hyperthyroidism or use of thyroid medication, glaucoma; diabetes mellitus patients may become difficult to regulate because of fluctuation of blood glucose levels; simultaneous use of MAO inhibitors; simultaneous use of thyroid medication Simultaneous use of MAO inhibitors; diabetes mellitus patients may be difficult to regulate

Clomipramine (Clomicalm)

C: 2-3 mg/kg bid F: 0.5-1 mg/kg sid

Sedation, urine retention (cats), change in appetite, diarrhea, vomiting; also, lowering of seizure threshold and arrhythmias; drug should be given with food to reduce likelihood of gastrointestinal upset

Fluoxetine (Prozac) Paroxetine (Paxil)

1 mg/kg sid-bid 1 mg/kg sid-bid

Sertraline (Zoloft)

C: 1-3 mg/kg sid-bid

Sedation, increased anxiety, animal seems “withdrawn,” loss of appetite; possibly lowering of seizure threshold With all serotonin active drugs, there is the rare possibility of development of the serotonin syndrome; in the one case known to the author, an affected cat periodically crossed her front legs, abducted her hind legs, and carried her tail in a stiff (broomstick) position (Straub tail)

Abbreviations: C, canine; F, feline; bid, twice daily; sid, once daily; MAO, monamine oxidase.

distracted with a noise, a command is issued, and the animal is rewarded for obeying the command. A regular routine increases the predictability of the animal’s environment. It is particularly important that feeding and exercise become a consistent daily part of the owner’s routine. Sufficient exercise provided to dogs serves to fill their need for exploration and social interaction with other dogs, even if just by sniffing and leaving scent marks. Rotating toys maintains the animal’s interest in them and may provide an opportunity to reduce arousal. Particularly attractive toys, such as food dispensing toys, can be given at times when the performance of the compulsive behavior is likely. In most cases, drug therapy may prove necessary or at least facilitate treatment. Pharmacologic intervention is most likely achieved with serotonin reuptake inhibitors, although it may take 4 weeks or longer to see an effect. A clinical trial involving 51 dogs with a variety of compulsive behaviors has proven the effectiveness of the tricyclic antidepressant clomipramine.15 A case series suggested effectiveness of clomipramine for tail chasing in Terriers.17 Clinical trials on cases of acral lick dermatitis have been performed for clomipramine, fluoxetine, and sertraline.23 Paroxetine has also been used clinically, but its effect has not been evaluated. We usually give the drug until at least 3 weeks after it seems to have had a satisfactory effect and then wean off gradually over at least 3 weeks by reducing dose but maintaining dosing frequency. If the behavior reappears during the weaning process, the dose is increased again and maintained at the effective level

for some time before resuming weaning. Weaning is important so as to avoid a rebound effect. Clomipramine can be combined with fluoxetine to slow down its metabolism. Tricyclics other than clomipramine or other anxiolytic drugs, such as benzodiazepines or buspirone, are unlikely to have any effect on CD on their own, and their use in drug combination therapy has not been evaluated in dogs. ␤-endorphin antagonists have been used experimentally,21 but most are injectables and have a short half-life,24 and their use for clinical cases is not practical. The dopamine antagonist haloperidol has also not been proven effective in practice, most likely because an appropriate dosing regimen has not been established. Drugs, dosages, contraindications, and side effects are summarized in Table 1. The main goal of drug treatment is to reduce the frequency of the compulsive behavior to the point that behavioral modification (ie, response substitution) becomes practical. In dogs, the patient is initially trained with positive reinforcement to perform a desirable behavior that is incompatible with (ie, cannot be performed at the same time as) the compulsive behavior. Whenever the dog cannot be supervised, it is put into a situation where it cannot perform the compulsive behavior (eg, the dog can be crated if it does not perform the behavior in the crate). As often as the dog can be closely supervised (we often recommend keeping the dog on a leash), it is put in the situation in which it is likely to perform the behavior. Every time the dog shows any inclination to perform the compulsive behavior, it is distracted (if neces-

Compulsive disorder in dogs and cats sary, by pulling on a leash connected to a head halter). The command for the alternate behavior is then given. The dog either performs or is made to perform the alternate behavior and is then rewarded. The reward can be progressively delayed so that the dog has to stay in the chosen position for increasingly longer times before the reward is given. Some serious cases of CD have been treated successfully with this behavioral modification technique alone (ie, without the use of drugs). The distraction is important. If the dog is not distracted before a command (ie, attention) is given, the treatment attempt could result in aggravation of the problem through inadvertent reinforcement of the behavior. In cats, we recommend a similar program. The cat is continuously supervised or placed in a position in which it does not perform the behavior. Every time the cat is about to perform the compulsive behavior, it is distracted (startled), and its attention is then reoriented by throwing a toy. Cats can also be clicker-trained and then treated as described for dogs.

Prognosis Analysis of a referral case load showed that approximately two thirds of cases improved to the client’s satisfaction and that outcome was negatively affected by problem duration.25 It is therefore important to treat CD as early as possible.

Acknowledgement The author thanks Dr Dianne Bevier, Purdue University, and Dr Elizabeth Klopp, University of Illinois, for their help with dermatologic and neurologic differentials, respectively.

References 1. Lawrence AB, Rushen J (eds): Stereotypic animal behavior. Oxon, CAB International, 1993 2. Wiepkema PR: Abnormal behaviours in farm animals: ethological implications. Neth J Zool 35:279-299, 1995 3. Hinde RA: Animal behavior (ed 2). New York, McGraw Hill, 1970, pp 396-421 4. Oedberg FO: Behavioral responses to stress in farm animals, in Wiepkema PR, van Adrichem PWM (eds): Biology of stress in farm animals: an integrative approach. Seminar in the CEC programme of coordination of research on animal welfare. Oosterbeek, Netherlands, April 17-18, 1986. Boston, Martinus Nijhoff, 1987, pp 135-150 5. Luescher UA, McKeown DB, Halip J: Stereotypic and obsessive-compulsive disorders in dogs and cats. Vet Clin North Am Small Anim Pract 21:401-413, 1991 6. Goldberger E, Rapoport JL: Canine acral lick dermatitis: response to the antiobsessional drug clomipramine. J Am Anim Hosp Assoc 27:179182, 1990

239 7. Overall KL: Recognition, diagnosis and management of obsessive-compulsive disorders. Part I. Canine Pract 17:40-44, 1992 8. Hewson CJ, Luescher UA: Compulsive disorder in dogs, in Voith VL, Borchelt PL (eds): Readings in companion animal behavior. Trenton, Veterinary Learning Systems, 1996, pp 153-158 9. Summerfeldt L, Richter MA, Anthony MM, Swinson RP: Symptom structure in obsessive compulsive disorder: a confirmatory analytic study. Behav Res Ther 37:297-311, 1999 10. Anthony MM, Downie F, Swinson RP: Diagnostic issues and epidemiology in obsessive-compulsive disorder, in Swinson PR, Anthony MM, Rachman S, Richter MA (eds): Obsessive compulsive disorder. Theory, research and treatment. London, The Guilford Press, 1998, pp 3-32 11. Rachman S, Shafran R: Cognitive and behavioral features of obsessivecompulsive disorder, in Swinson PR, Anthony MM, Rachman S, Richter MA (eds): Obsessive compulsive disorder. Theory, research and treatment. London, The Guilford Press, 1997, pp 51-78 12. Hewson CJ: Clomipramine in dogs: pharmacokinetics, neurochemical effects, and efficacy in compulsive disorder [PhD thesis]. Guelph, Ontario Veterinary College, 1998 13. Hartigan PJ: Compulsive tail chasing in the dog: a mini-review. Ir Vet J 53:261-264, 2000 14. Kennes D, Odberg FO, Bouquet Y, DeRycke PH: Changes in naloxone and haloperidol effects during the development of captivity induced jumping stereotypy in bank voles. J Pharmacol 153:19-24, 1988 15. Hewson CJ, Parent JM, Conlon PD, Luescher UA, Ball RO: Efficacy of clomipramine in the treatment of canine compulsive disorder: a randomized, placebo-controlled, double blind clinical trial. JAVMA 213: 1760-1766, 1998 16. Vanderbroek I, Odberg FO, Caemaert J: Microdialysis study of the caudate nucleus of stereotyping and non-stereotyping bank voles, in Proceedings of the 29th International Congress of the International Society of Applied Ethology. Potters Bar, England, Universities Federation for Animal Welfare, 1995, p 245 17. Moon-Fanelli AA, Dodman NH: Description and development of compulsive tail chasing in terriers and response to clomipramine treatment. JAVMA 212:1252-1257, 1998 18. Cabib S: Neurobiological basis of stereotypies, in Lawrence AB, Rushen J (eds): Stereotypic animal behavior: fundamentals and applications to welfare. Wallingford, CAB International, 1993, pp 119-145 19. Oliver JE, Lorenz MD: Neurological history and examination, in Handbook of veterinary neurology (ed 2): Philadelphia, WB Saunders, 1993, pp 9-10 20. Dodman NH, Knowles KE, Shuster L, Moon-Fanelli AA, Tidwell AS, Keen CL: Behavioral changes associated with suspected complex partial seizures in Bull Terriers. JAVMA 208:688-691, 1996 21. Dodman NH, Shuster L, White SD, et al: Use of narcotic antagonists to modify stereotypic self-licking, self-chewing and scratching behavior in dogs. JAVMA 193:815-819, 1988 22. Reisner I: The pathophysiological basis of behavior problems. Vet Clin North Am Small Anim Pract 21:207-224, 1991 23. Rapoport JL, Ryland DH, Kriete M: Drug treatment of canine acral lick: an animal model of obsessive compulsive disorder. Arch Gen Psychiatry 49:517-521, 1992 24. Garrett ER, el-Koussi AEA: Pharmacokinetics of morphine and its surrogates. V. Naltrexone and naltrexone conjugate pharmacokinetics in the dog as a function of dose. J Pharm Sci 74:50-56, 1985 25. Luescher AU: Factors affecting the outcome of behavioral treatment. Presented at the 134th Meeting of the American Animal Hospital Association, San Diego, CA, July, 1997