Metaphors used to describe the human brain, such as that of a highly efficient computer, often convey an image of impeccable organization and control. Yet the thoughts, feelings, and urges produced by the brain are actually considerably more chaotic, with little control on the part of the person experiencing them. History is replete with descriptions of individuals who struggled with or succumbed to uncontrollable thoughts that ran amok, overwhelming the capacity for organized thought or behavior. Where in the past such individuals may have been considered the victims of an evil force, such as a demon or a curse, the modern science of mental health views them as suffering from a neurologic condition stemming from the physical functioning of the brain. Attributing intrusive and uncontrollable thoughts and feelings to the actions of the central nervous system also enables the identification of a continuum in these processes—from the normative and healthy to the clinical and psychopathologic. Indeed, symptoms characteristic of obsessive-compulsive disorder (OCD) are present at some level in the general population and even somewhat elevated levels of these patterns are considered normative at some developmental stages (Garcia-Soriano et al., 2011).

Freud is often credited with providing the first cohesive description of OCD in the modern era, in his case history of a patient he nicknamed the Rat Man (Freud, 1997). The actual identity of the Rat Man, whom Freud described as a “youngish man of university education,” remains in some question, but he may have been a lawyer by the name of Ernst Lanzer. The Rat Man was treated by Freud over several months, starting in 1907, because of intrusive obsessive thoughts and compulsive urges he had experienced since childhood including the eponymous obsessive thought about a form of torture involving rats. Freud provided a typically psychoanalytic explanation for the symptoms, centering around forbidden sexual and aggressive wishes and the defenses against them, and claimed at least partial success for the treatment. Despite the differences between Freud’s approach and those more common today, the case of the Rat Man highlights many aspects of the disorder that are still seen as hallmark features.

OCD is the clinical term for a condition characterized by the presence of obsessions and/or compulsions. Obsessions are thoughts, urges, impulses, images, or other mental content that are intrusive in that they enter the mind unbidden and repeatedly, causing distress and impairing normal function. In children in particular, obsessions may be described as a “voice” in the mind but should be distinguished from auditory hallucinations. Children with OCD who describe their obsessions as a voice are generally able to recognize that the thoughts are emerging from their own mind and do not expect others to hear them as well (Selles et al., 2018).

Compulsions are behaviors the person feels compelled to perform, usually in rigid and repetitive fashion and often with the goal of alleviating distress stemming from the presence of an obsession. Obsessive behaviors tend to be highly ritualized and can be external behaviors performed with the body or internal behaviors performed in the mind only. Some common examples of external compulsions include saying certain words, touching or arranging objects, repeating behaviors unnecessarily (e.g., washing or cleaning), and checking that some condition is met. Examples of internal compulsions can include repeating words in the mind, counting, mentally rehearsing or reviewing, and praying. Compulsions are often, but not always, directly linked to a particular obsession. For example, a child with obsessive thoughts about harm relating to germs or contamination may feel compelled to engage in handwashing rituals whenever the obsessive thought arises. But a child without such an obsession may likewise exhibit excessive handwashing. Even when the compulsion follows a particular obsession, the content of the thought will not necessarily be directly related to the form of the obsession. For example, a child with obsessions about engaging in a forbidden, inappropriate, or harmful behavior may likewise engage in handwashing in response to the thoughts.

Obsessions and compulsions can take any form and center around any domain of content, but certain themes or “dimensions” of OCD have been identified, and most OCD symptoms will fall into these broad categories (Leckman et al., 2005). Common themes for obsessions include thoughts about harm (either befalling or perpetrated by the individual with OCD), religion, sex (less common, but not absent in young children), symmetry, numbers (e.g., magical or “good” and “bad” numbers), contamination (by germs, chemicals, or other things), and doubting (e.g., doubting whether a certain behavior such as shutting off a light was actually completed). Common themes for compulsions include checking, arranging, repeating (can include physical, verbal, or mental repetition), and cleaning.

At least a moderate level of insight, or the ability to recognize that the obsessive thoughts are unrealistic and the compulsive behaviors unnecessary, is present in the majority of individuals with OCD, including children. In a large study aggregating data from multiple sources internationally, complete lack of insight was present in only 1.4% of children with OCD, whereas approximately 90% of children had insight that was categorized as fair or better (Leckman et al., 2005).

The broad spectrum of OCD symptoms, from the normative to the highly debilitating, means that the mere presence of some such symptoms cannot be taken as indicative of psychopathology. For example, a preference for repetition, a tendency toward various forms of magical thinking, certain superstitious-like behaviors, and repeated checking behaviors are all common during childhood. Likewise, young children often manifest a preoccupation with symmetry and rules and with guilt or lying that can be similar to symptoms of OCD (Leckman et al., 2005) (Box 13.1).

Establishing a diagnosis of OCD therefore necessitates that the symptoms be developmentally unexpected and significantly impairing to some important area of functioning such as school, social interactions, or family relations or that they consume substantial time each day (American Psychiatric Association, 2013). Determining the actual amount of time consumed by OCD symptoms can be challenging however, in particular for young children or when the symptoms are primarily internal mental events.

The impairment associated with OCD, much like the severity of symptoms, can range very broadly. In some cases, only certain aspects of functioning are meaningfully impaired and overall function is well preserved. For example, a child with OCD may be chronically late to school or other engagements because of compulsive rituals and slowness but may function at a high level once there.

Children with OCD may be high achievers in school and social interactions can also be good, though in many cases they are impacted by the symptoms. In other cases, the impairment is considerably broader and almost every aspect of function is impacted. In the most severe cases, the disorder can be completely debilitating, preventing essentially any age-appropriate function in or outside of the home. The repetition of certain rituals can also lead to physical damage such as the macerations that can occur from excessive handwashing (Box 13.2).

As with other childhood conditions, impairment is not limited to the child alone and overall family functioning is frequently significantly impaired. A child with OCD can place functional and economic burden on a family. Relations often become strained because of a child’s symptoms and parents may miss work because of the need to remain with a child. Some symptoms can also lead to extra expenses as parents purchase special items or buy larger quantities of items than they otherwise would.

Parents and others in the home typically engage in family accommodation of children’s OCD symptoms (Shimshoni et al., 2019). The term accommodation refers to any changes to the parents’ behavior aimed at helping their child to avoid or lessen symptom-related distress. Common forms of accommodation in OCD include parents purchasing special items, engaging in compulsive rituals themselves, and listening to a child’s “confessions.” For example, parents might carry a child physically because their OCD makes them unwilling to walk in certain places or touch the floor, or they might answer repeated questions relating to the child’s obsessive content. The accommodation can be extremely time consuming and children will often react negatively, including with anger or aggression, to any attempt on the parents’ part to refrain from accommodating. Parents typically report high levels of distress stemming from the need to accommodate their child. Research also consistently links higher levels of accommodation to worse symptoms and indicates that accommodation is associated with worse treatment outcomes for both psychosocial and pharmacologic treatment interventions (Strauss et al., 2015).

Given the heterogeneity of its presentation and the broad spectrum of symptoms across both form and severity, it is not surprising that establishing the actual prevalence rates of OCD in children and adolescents, and indeed at any age, is not straightforward and estimates have ranged quite broadly. It is likely that actual lifetime prevalence is between 1% and 2% and approximately equal for males and females, though average age of onset may be earlier for boys than for girls, leading to higher prevalence of OCD in male children (Rapoport et al., 2000). Rates of OCD in different demographic groups, including race and ethnicity, are comparable.

In general, age of onset for OCD appears to follow a bimodal distribution with two peak points. Early-onset OCD begins in the prepubertal period, usually between the ages of 6 and 10. Later-onset OCD usually begins toward the end of the teenage years or in early adulthood (Chabane et al., 2005).

Comorbidity is very common in OCD, with clinical samples showing a majority of cases having at least one comorbid psychiatric condition (Storch et al., 2008). Frequently comorbid
with OCD are anxiety disorders, depression, attention and behavior problems, and other OCD-related conditions such as tic disorders and hoarding. The presence of comorbidity can increase the burden of the condition and is associated with more severe symptoms, greater impairment, and worse treatment outcomes (Geller, Biederman, Stewart, Mullin, Farrell, et al., 2003).

The etiology of OCD is a matter of ongoing research; its understanding is hampered by aspects of the condition and by methodologic limitations. Among these are the heterogeneity of the disorder and the possibility for multiple etiologically distinct subtypes, as well as small sample sizes in many studies and the variability in diagnostic and assessment tests used.

Genetic research supports an important role for heritability in the vulnerability to OCD. Familial studies show higher rates of OCD among first-degree relatives of individuals with OCD, compared with the general population, as well as higher rates of other OCD-related conditions such as tics, trichotillomania, and body dysmorphic disorder (Grabe et al., 2006; Pauls et al., 1995). Twin studies have also found that monozygotic (identical) twins are significantly more likely to share a diagnosis of OCD than are dizygotic (fraternal) twins (Hudziak et al., 2004). Genome-wide association studies have also supported significant heritability for OCD and are being used, along with other methodologies, to identify specific genes implicated in the etiology of the disorder (Shugart et al., 2006).