Recently an owner came to my office with the complaint of tail chasing in her dog. How can I determine if this is a compulsive disorder?

Compulsive behaviors are defined as "acts that are repetitive, constant, and appear to serve no obvious purpose."1 Compulsive disorders arise from normal, species-typical behaviors, such as locomotion, grooming, or vocalization; are often performed at persistently high levels; occur out of context; and may be self-injurious. It may appear that the animal has no control over the initiation and maintenance of the behavior. 

In susceptible individuals, situations causing frustration, conflict, or anxiety may precipitate compulsive behaviors, which may resemble behaviors that are associated with medical problems. Therefore, a good physical examination and appropriate laboratory testing or imaging are essential before a compulsive disorder can be diagnosed. 

Types of Disorders
Compulsive disorders can be grouped into 5 categories that may overlap:
• Oral: chewing feet or nails, flank sucking, licking (granulomas), air licking, fly snapping, polyphagia, polydipsia, eating inappropriate objects
• Vocalization: rhythmic barking, barking at food, snarling at self
• Hallucinatory: staring, fly chasing, prey searching and pouncing, shadow and light chasing
• Locomotory: circling, whirling, spinning, tail chasing, fence-line running, pacing
• Aggressive: vicious biting of feet or tail with or without growling, unpredictable aggression toward humans, aggression directed at inanimate objects.2

Genetic components are possible; certain breeds are overrepresented in some types of compulsive behaviors (eg, flank sucking in Doberman pinschers, tail chasing in herding breeds).

The average age of onset is between 12 and 36 months. The pet engages in a repetitive, unvarying sequence of behaviors and may perform this sequence excessively, such that it interferes with normal functioning. The behavior may first be exhibited in situations of conflict or frustration (as might occur when the dog is faced with 2 competing behavioral patterns-eg, approach or avoidance) and later may be generalized to other high-arousal contexts. Over time, the bouts may become more frequent, last longer, and occur with increased intensity. The pet may be unresponsive to attempts to interrupt the sequence of behaviors, and often a multitude of interventions have been unsuccessful. 

History Taking
A behavioral history should include the daily management routine for the pet, household composition, daily interactions with family members, and physical and mental stimulation provided. Information from the owner and personal observation of the pet should be used to establish the basic temperament: for example, reactive, anxious, confident, or calm. The date of onset, the progression of the problem behavior, and the current presentation should be explored. 

Determine the frequency, duration, and intensity of the behavior to help assess treatment response. Ability to interrupt the behavior may help rule out a seizure condition. Are any triggers for the behavior readily identifiable? Owner responses should be explored in detail, as well as pet responses to interventions. Video recordings are useful not only to visualize the behavior but also to attempt to establish whether the behavior occurs in the owner's absence (eg, when owner is away from home or the pet is in the yard). 

A detailed description of the 2 or 3 most recent episodes is necessary and should include the time of day, the people present, a description of the behavior, the owner's reaction, and pet actions when the behavior has terminated. Any other concurrent behavioral disorders, such as aggression, separation anxiety, noise sensitivities, and attention seeking, should be identified and concurrent treatment instituted if other disorders exist.

Differential Diagnosis
The differential diagnoses include normal response to an acutely stressful situation, attention seeking, seizures, central brain lesions, sensory neuropathies, metabolic diseases, infectious diseases, toxin exposure, dermatologic disease, trauma, and degenerative disease. A good physical examination, laboratory testing, dermatologic workup, neurologic examination, and video recording can help sort through the various possibilities to arrive at a final diagnosis. 

Treatment encompasses several modalities. Because stress and anxiety may contribute, controlling the environment and decreasing stress are important. Any identified triggers should be avoided. If that is not possible, the animal should be desensitized and counter-conditioned to the trigger. All punishment must be avoided because it is ineffective in changing the behavior and increases stress, anxiety, fear, and perhaps aggression. Owners should strive for positive interactions, and all training should use positive reinforcement.

Creating an environment that is predictable, safe, and calm will help to diminish stress and anxiety. The daily performance of routine obedience tasks helps create a structure for pet-owner interactions. Frequently it helps to have interactions between the owner and the dog on a command-response basis. These predictable interactions allow the animal to have control over what happens to it and choices in outcomes.

Earning attention by being calm and quiet is effective for many dogs, especially when owners also ignore attention-seeking behaviors. A regular routine for exercise, attention, feeding, and play should be provided daily. Activities that involve normal canine behaviors should be encouraged with toys and walks. Chewing, sniffing, and exploration should be encouraged with feeder toys, games, and outings. 

Training the dog to perform a desirable behavior that is incompatible with the compulsive behavior is useful (ie, response substitution). Substitute behaviors include settling and relaxing, sit and stay, or focusing on the owner. The use of a head collar and leash can help increase control and divert the dog at the first sign of the compulsive behavior, after which the pet is rewarded for performing the alternative task. 

Pharmacologic Intervention
Medication is useful for reducing the compulsive response and facilitating treatment. SSRIs are most useful but may take 2 to 4 weeks until an effect is noted. The goal of medication is to reduce the frequency of the compulsive behavior so that new behaviors can be taught and substituted in situations in which the compulsive behavior was previously performed. 

• Fluoxetine:3May take 2 to 4 weeks until effect is noted. Gradually increase the dose over several weeks if no effect occurs after 1 month or so. Common side effects include gastrointestinal effects, sedation, lethargy, irritation, insomnia, and anorexia. Should  not be used with monoamine oxidase inhibitors, other SSRIs, or TCAs.
• Clomipramine:4 The dose is gradually increased over several weeks if no effect is noted. Side effects include anticholinergic effects, urine retention, change in appetite, gastrointestinal signs, lowering of the seizure threshold, and cardiotoxic effects. If the patient is concurrently being treated for hypothyroidism, clomipramine can produce signs of hypothyroidism. The drug should not be used with monoamine oxidase inhibitors or SSRIs.

Response to intervention varies. Luescher5 found that two thirds of owners whose pets were treated with medication and behavior modification were satisfied with the outcome. In the same study, he found that outcome was negatively affected by the duration of the problem.

TX at a glance

Identify, then avoid, sources of stress and anxiety.

Create a calm, predictable environment with daily interactions and appropriate activities.

Suggest interactions between the owner and pet that are predictable and reward-based.

Avoid all punishment and reprimands; ignore or redirect unwanted behaviors.

Administer medication if needed for severe cases.   

Drug                         Drug Class                     Dose Range                                     Frequency             Route

Fluoxetine              SSRI                                 1-2 mg/kg (see Luescher3)           Q 24 H                   Oral

Clomipramine      Tricyclic depressant      1-3 mg/kg (see Hewson et al 4)    Q 12 H                   Oral

SSRI = selective serotonin reuptake inhibitor; TCA = tricyclic antidepressant