Obsessions are among the oldest mental symptoms for which there are detailed descriptions. Obsessions and compulsions were depicted as possession by the devil in 1467 in Malleus Malficarum (1) and described in the “Obsessi” of Paracelsus. In the 1600s, pious texts tell of extremes of religious doubting and “scrupulosity,” or excessive devotion (2). Pioneers of psychiatry like Esquirol (3), Maudsley (4), Freud (5), and Janet (6) took up this troubling and fascinating disorder and their writings reflect the prevailing philosophy of thought, motivation, and free will.

Two discoveries promoted OCD research in the last three decades. First, there was the discovery that medications that inhibit serotonin reuptake are effective for many OCD patients. Subsequently, powerful techniques for observing structures and measuring regional brain activity were applied to learn about brain function during performance of tasks tapping specific regions of interest. The effort to understand OCD has deepened our understanding of the prevalence, course, etiology, and pathology of these symptoms and along the way, broadened our knowledge of the neuroanatomy of voluntary cognitive functions and behavior.

Obsessions are unwanted thoughts, images, or impulses that are recognized as senseless or unnecessary, intrude into consciousness involuntarily, and cause functional impairment and distress. Despite this lack of control, a person with obsessions is aware that these thoughts originate in his or her own mental activity. Since they arise in the mind, obsessions can take the form of any mental event— simple repetitive words, thoughts, fears, memories, pictures, or elaborate dramatic scenes.

Compulsions are actions that are responses to a perceived internal obligation to follow certain rituals or rules; they too cause functional impairment. Compulsions may arise as direct consequences of obsessions or indirectly through efforts to ward off certain thoughts, impulses, or fears. Children often report that their compulsions do not have a preceding mental component. Like obsessions, compulsions are often viewed as being unnecessary, excessive, senseless, involuntary, or forced. Individuals suffering from compulsions will often elaborate a variety of precise rules for the chronology, rate, order, duration, and number of repetitions of their acts.

These definitions reflect three critical concepts that are relevant to the differential diagnosis. An essential criterion is
functional impairment as a consequence of symptoms. Two others draw on classic definitions (4,7): Individuals feel that they are being forced or controlled by the symptoms, while they possess insight into the senselessness or excessiveness of their thoughts or acts. Although most patients see their compulsions as unnecessary or their thoughts as senseless, some have this only intermittently. Consequently, some investigators have reservations about the criterion that patients possess insight about their illness. Insel and Akiskal (8) and Lelliott and coworkers (9) reported on severely impaired patients who at times doubted the need to perform their rituals or thought their behaviors were senseless and, at others, were convinced of their necessity to the point of near or actual psychotic proportions. DSM-IV criteria for obsessive-compulsive disorder (OCD) (Table 5.5.2.1) have been modified such that awareness of the senselessness or excess of the symptoms only must be present at some phase of the illness. For children, this criterion is set aside altogether.

Few studies differentiate between participants with childhood- and adolescent-onset OCD. Therefore, in this chapter, “child,” “childhood,” or “children” will be used to signify children and adolescents. There are studies that have sampled adolescent subjects only. When this is so, the more exclusive term will be employed.

The prevalence of OCD in childhood should be understood in the context of the high prevalence of subclinical obsessions or compulsions in the population. Evans and coworkers (10) sent out mailings to parents of children less than 6 years old and found that urges to make things “just right” and preoccupations with symmetry and rules were very common in this unselected population. It was notable that these concerns declined as children entered grade school age. To learn about the prevalence of obsessive and/or compulsive symptoms and compare prevalences across development, Zohar and Bruno (11) used self-report measures for a study of 1,083 children attending grades four, six, and eight. As predicted, a large segment of the pediatric population confirmed experiencing these features. Sixty percent of fourth graders reported preoccupations with guilt about lying and engaging in checking behaviors and 50% reported contamination and germ fears. By eighth grade, rates for these concerns declined to 40%, but 60% of eighth graders reported worries about cleanliness and 50% noted intrusive rude thoughts. Mean scores across the age range on the Maudsley Obsessive Compulsive Inventory were 11–12.5/30 in this population; like Evans and coworkers’ (10) finding from a younger population, rates of behaviors and symptoms declined over time. A subgroup of eighth graders had high symptom scores (greater than 2 standard deviations from the mean) and reported high levels of anxiety. The authors suggest that this small group (4%) represented a clinically at-risk group because the large number of symptoms and elevated state and trait anxiety were such a contrast to the decline in both in their age-mates.

Twenty years after the Epidemiologic Catchment Area (ECA) survey (12), there continue to be important disagreements over the most reliable prevalence rate for OCD. Significant disparities and varied methods have yielded figures between 0.5 and 3%. It is useful to place these figures in the context of adult epidemiological reports.

The early work (13), using weak methods by current standards, reported a prevalence of 0.05% for adult OCD. The scarcity of OCD was predominant until 1984, when the ECA survey reported surprising prevalences of 1.2–3.29% (12). Subsequent examination of these high rates uncovered weak concordances for OCD. Among all the diagnoses in the ECA study, the concordance between diagnoses derived from lay interviewers and trained clinicians for OCD were the poorest (14,15,16). Lay interviews employing the Diagnostic Interview Schedule (DIS) rely on simple yes or no responses to queries about the presence of broadly defined obsessions or compulsions. These are not reliable measures for actual clinical cases of obsessive-compulsive disorder. Helzer and co-workers (15) went on to say that results from community surveys, where many subjects cluster at the “threshold of the diagnostic definition,” will be unreliable because the response to a single probe carries too much weight. Karno and coworkers (17) reanalyzed ECA data, and prevalence rates were sustained despite the flawed methodology. False negatives balanced false positives.

In an effort to learn more about this problem, Nelson and Rice (18) used ECA methods and interviewed a community sample at two intervals separated by 12 months. The 1-year stability of the diagnosis of OCD was “very low.” Only 20% of those responding to “ever having symptoms” at Time 1 reported, “ever having symptoms” at Time 2. They concluded that “the DIS diagnosis of obsessive-compulsive disorder possesses extremely limited validity.”

Stein and coworkers (19) employed a different measure (the Comprehensive International Diagnosis Interview) and DSM-IV criteria. Again, rates derived from lay interviews revealed 22–25% of adults expressed having obsessions or compulsions. However, when clinicians reviewed lay interviews, the rates dropped seven-fold (to 0.7%). They also examined rates of “subclinical OCD” in which criteria were met for symptoms, but not impairment in DSM-IV. Rates for this subclinical syndrome were roughly equivalent to clinical OCD (0.6%). Stein and coworkers (19) concluded, like Karno (17) and Nestadt (16), that lay interviews led to many false-positive diagnoses.