rent obsessive thoughts or repetitive behaviors called compulsions that the individual feels he or she must perform. Young children are more often characterized by compulsions than by obsessions. Some children spend considerable time involved in elaborate rituals surrounding cleaning or checking routines, providing vague justifications for these behaviors. Adolescents are both more willing and better able to describe the obsessive thoughts that accompany their compulsions. Patients with OCD sometimes exhibit tics and attention deficit hyperactivity disorder (ADHD). Although OCD had been considered a rare condition, recent research suggests that as many as 1% of children exhibit this disorder.

A diagnosis of generalized anxiety disorder (GAD) is given to adolescents who worry about a variety of events or life circumstances—usually schoolwork, appearance, money, or their future. Age of onset of GAD is usually later than for most other disorders, although many patients report having been anxious for many years. Further, GAD is likely to be comorbid with other symptoms, but the primary symptom is a chronic state of worry, rather than chronically avoidant behavior.

The essential feature of panic disorder is the repeated experience of intense fear of impending doom or danger following the unprovoked experience of bodily symptoms, especially rapid heart rate, shortness of breath, choking sensations, and sweating, or a feeling of depersonalization. The onset of this disorder is usually in late adolescence or early adulthood. Some patients with panic attacks will develop a fear of leaving home to avoid a panic attack; these patients are called agoraphobic. Panic disorder usually begins with sporadic isolated episodes of anxiety that accompany a panic attack and becomes a full-blown panic disorder between adolescence and adulthood (Pine, Cohen, Gurlet, Brook, & Ma, 1998).

Although young children can have an occasional panic reaction, it is unclear whether these attacks are accompanied by thoughts of impending danger. Moreover, it is extremely rare for children to experience panic reactions spontaneously in the absence of a trigger. Spontaneous panic attacks are the essential element of the diagnosis. Hence, there is some controversy over the degree to which panic disorder occurs in preadolescents. If this disorder does occur in children, it is relatively infrequent. Some investigators believe that the essential missing component in early childhood is the unprovoked change in bodily sensations, rather than the ability to impose a catastrophic interpretation.

Unlike the other anxiety disorders, a diagnosis of posttraumatic stress disorder (PTSD) rests on a clearer causal sequence in which a person is first exposed to a traumatic event, feels frightened because of the threat to personal integrity, and then develops the disorder. Patients with PTSD present three kinds of symptoms. First, the patient must suffer from episodes of reexperiencing the traumatic event, which can include recollections of the event manifested in flashbacks or recurring dreams. Second, patients must attempt to avoid any event or place associated with the trauma, and the avoidance is accompanied by feelings of numbness or reduced responsivity. Finally, PTSD patients must experience signs of increased physiological arousal, especially difficulty falling asleep, increased irritability, or exaggerated startle. As with panic disorder, there is some debate over whether children exposed to trauma manifest all three symptoms. Children are likely to display separation anxiety disorder following a traumatic event. Nonetheless, the diagnostic criteria for PTSD in the DSM-IV are the same for children and adults.

The most prevalent diagnoses are DSM-III-R overanxious disorder (OAD) (0.5% to 7.1% with a median of 3.6%), DSM-IV specific phobias (0.1% to 12.2% with a median of 3.5%), and social phobia (0.3% to 15.1% with a median of 3.5%). Panic disorder (0.1% to 3.1%, median of 1.1%) and OCD (0.1% to 7.1%, median of 0.6%) are far less common. The use of adult diagnostic instruments such as the Disorders Interview Schedule (DIS) produce higher rates of specific and social phobias, agoraphobia, and OCD. By contrast, instruments designed specifically for children yield lower prevalence rates. Thus caution should be exercised when adult diagnostic instruments are used with children.

The relation between the diagnosis and everyday functioning remains a focus of controversy. Health maintenance organizations, insurance companies, and governmental agencies are concerned with whether children diagnosed with anxiety disorder require treatment (Costello, Burns, Angold, & Leaf, 1993). One perspective

requires that a child show significant impairment or disability to receive a diagnosis, in which disability can refer to a particular symptom or the entire syndrome. Clinicians could rate a child's psychological functioning but fail to make a clinical diagnosis (Hodges, Doucette-Gates, & Liao, 1999; Shaffer et al., 1983).

The prevalence of anxiety disorders varies according to whether disability is or is not part of the definition. If a child must meet the criteria for a diagnostically relevant symptom as well as impairment in everyday functioning, the prevalence of a diagnosis is reduced by two-thirds. Further, requiring both specific impairment as well as severe scores on the Children's Global Assessment Scale (CGAS; Shaffer, Fisher, Dulcan, & Davies, 1996) reduced the prevalence of disorder by almost 90%. The prevalence of simple phobia was affected most severely; the prevalence fell from 21.6% if no impairment was required to an estimate of only 0.7% when impairment in daily functioning was required. Thus, all estimates of the frequency of the anxiety disorders depend in a serious way on the source of evidence and the criteria adopted. There is no “correct” prevalence in the sense that there is a correct height, in meters, for the Empire State Building.

Most investigators report that girls are more likely than boys to have an anxiety disorder. For example, more girls than boys between ages 9 and 16 years participating in the Great Smoky Mountains Study had an anxiety disorder (12.1% vs. 7.7%; Costello et al., 2004). Three studies revealed more phobias in girls, two reported more panic disorder and agoraphobia in girls, and only one study found more separation anxiety disorder and OAD in girls than in boys. In one of the few studies that examined the potential confounding factors linked to gender, the excess of anxiety disorder in girls was not eliminated after controlling for 15 possible confounding factors (Lewinsohn, Gotlib, Lewinsohn, Seeley, & Allen, 1998). One confound was the fact that the child's age is often correlated with the time frame used to estimate symptoms. Investigators who used 3-month prevalence rates reported the lowest prevalence but studied the youngest subjects. By contrast, investigators using 12-month estimates had the highest prevalence but worked with the oldest children. In the Great Smoky Mountains Study the prevalence of separation anxiety decreased with age, whereas social phobia, agoraphobia, and panic disorder increased with age. It is difficult to draw conclusions about gender differences in the fears, worries, and anxieties of clinic-referred samples (either clinically anxious samples or other types of clinical samples) given the limited amount of research that has been conducted. Further research in this area is of critical importance (see Silverman & Carter, in press).

On any one day, between 3% and 5% of children and adolescents suffer from an anxiety disorder. Rates of GAD and specific phobias remain constant across childhood and adolescence. Although girls are more likely than boys to have an anxiety disorder, the gender difference is not as marked in the general population as it is in clinical samples, perhaps because boys are less likely to be referred for treatment. Numerous studies have demonstrated that girls who mature earlier than their peers exhibit higher rates of anxiety symptoms and disorders (e.g., Caspi & Moffitt, 1991); such findings have not been obtained with boys.

Comorbidity among the anxiety disorders has been a problem for nosology, epidemiology, diagnosis, and treatment. The high level of comorbidity in clinical samples is mirrored in community samples (Brady & Kendall, 1992; Kendall & Clarkin, 1992; Kendall, Kortlander, Chansky, & Brady, 1992; Table 9.2). A review by Costello et al. (2004) yielded equivocal results because not all diagnoses were present in every study, there was a lack of consensus regarding controls for comorbidity, and concurrent comorbidity and sequential comorbidity were not always distinguished.