Clinical Manifestations

A child’s presentation depends on the nature of the habit and level of the child’s awareness of the behavior. Habit behaviors can be described as either automatic or focused, depending on the child’s level of awareness. It has been suggested that a focused style (e.g., having awareness and receiving gratification from performing the behavior) is associated with higher levels of co-occurring habits. This style in hair pulling has been linked with increased depression, anxiety, and impairment in functioning, particularly during stressful events and onset of puberty.

Teeth grinding, or bruxism, is common, can begin in the first 5 yr of life, and may be associated with daytime anxiety. Untreated bruxism can cause problems with dental occlusion. Helping the child find ways to reduce anxiety might relieve the problem; bedtime can be made more relaxing by reading or talking with the child and allowing the child to discuss fears. Praise and other emotional support are useful. Persistent bruxism requires referral to a dentist and can manifest as muscular or temporomandibular joint pain.

Thumb sucking is normal in infancy and toddlerhood. Like other rhythmic patterns of behavior, thumb sucking is self-soothing. Basic behavioral management, including encouraging parents to ignore thumb sucking and instead focus on providing the child with praise for substitute behaviors, is often effective treatment. Simple reinforcers, such as giving the child a sticker for each block of time that he or she does not suck the thumb, can also be considered. Although some literature suggests that the use of noxious agents (bitter salves) may be effective in controlling thumb sucking, this approach should rarely be necessary.

Trichotillomania is the repetitive pulling of hair resulting in loss and strand breakage of hair (Chapter 654). The usual age of onset of trichotillomania is around 13 yr, although preschoolers have been described with this disorder. Children with trichotillomania have an increasing sense of tension immediately before pulling or when resisting the behavior, followed by pleasure or relief when pulling out the hair. The prevalence of trichotillomania in children is not well known but is believed to be 1-2% in college students. Although trichotillomania often remits spontaneously, treatment of those whose disorder has been present for >6 mo is unlikely to remit and requires behavioral treatment. Selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine have some success as adjuncts.

Diagnosis and Differential Diagnosis

The child should be screened for current and past psychiatric symptoms (particularly anxiety, obsessions, compulsions, and depression) along with any accompanying functional limitations. The child should be examined for any significant physical injury from habit behaviors.

The differential diagnosis includes the stereotypic movements associated with mental retardation and pervasive developmental disorders. Compulsions with obsessive-compulsive disorder (OCD) and tic disorders as well as involuntary movements associated with neurologic conditions must be considered. Developmentally appropriate self-stimulatory behaviors in young children and in persons with sensory deficits (e.g., blindness) are other considerations.

Epidemiology

Prevalence rates remain unclear given the various different manifestations of habits. Thumb sucking is common in infancy and in as many as 25% of children age 2 yr and 15% in children age 5 yr. Nail biting has a reported child prevalence as high as 45-60%. Bruxism has been observed in 5-30% of children and breath-holding spells in up to 4-5% of children younger than 8 yr. The prevalence of self-injurious behaviors in the context of mental retardation varies from 2-3% in the community to 25% of institutionalized adults with severe mental retardation.

Certain habit disorders are more common in children with developmental delays, particularly those with pervasive developmental disorders. Self-injurious habits, such as self-biting or head banging, can occur in up to 25% of normally developing toddlers, but they are almost invariably associated with developmental delays in children older than 5 yr. Habit disorders in developmentally disabled children are more refractory to treatment than those in typically developing children, and referral to a developmental pediatrician or child psychiatrist for behavioral and/or psychopharmacologic management is often indicated. The pediatrician must also rule out severe neglect, which is associated with repetitive rocking, spinning, or other stereotypies. Institutionalized children have the highest rates of these kinds of stereotypies.

Etiology

Although habit disorders are limited and diverse, given the wider variety of habit behaviors (hand shaking, head banging, mouthing objects, body rocking, skin picking), the literature is suggestive of repetitive abnormal grooming-like behaviors with possibly evolutionary ties to early human experience with adversity. Brain regions implicated are those involved in navigating human experience through unpredictable, anxiety-provoked emotional states (e.g., amygdala and hippocampus) as well as regions related to pleasure and reward seeking (e.g., nucleus accumbens). The latter involves the hypothesis that individuals experience some level of gratification from performing the habit behavior.

Treatment

Often the initial approach to helping children with habit behaviors is for the parents to ignore the behavior and not convey worry to their children. Generally these behaviors disappear with time and elimination of attention. If distress in the child or family, social isolation, and/or physical injury is occurring, then treatment is indicated.

Behavior therapy is the mainstay of treatment using a variety of strategies including habit reversal, relaxation training, self-monitoring, reinforcement, competing responses, negative practice, and, rarely, the use of aversive-tasting substances (for thumb sucking or nail biting). SSRIs are helpful in reducing repetitive behaviors, and they might play a role in particularly disabling and problematic behaviors, particularly those co-occurring with anxiety and obsessive-compulsive behaviors.