**4. Clinical features**

have a regression to anal period, and some defense mechanisms are commonly used like iso-

There is a little evidence about the cognitive mechanisms of OCD; it is thought that these mechanisms are similar in adults and children. According to cognitive theory, the basis of obsessions is catastrophic interpretation of unwanted and distressing thoughts, impulses, and images. Obsessions are creating anxiety, and by rituals, ruminations, or avoidances, this anxiety is tried to be reduced. For obsession treatment these misinterpretations must be corrected. Also in a study, maternal cognitive biases are found more relevant with younger children's

People with OCD seek medical help when their daily functionality is seriously compromised or they experience severe anxiety, and it has been reported that these individuals start seeking professional help after an average of 7 years from the onset of these symptoms. It was found that adolescents with OCD often hide their symptoms and delay seeking help due to several reasons such as inability to recognize their symptoms as disease manifestations, embarrassment, fear of being stigmatized by other people, and believing that what they experience is transient [29, 30]. Furthermore, because adolescents hide their symptoms, it is difficult to determine the actual prevalence of the disorder, and when they seek professional help, they may be misdiagnosed as depression or anxiety disorder due to not mentioning their symptoms [31].

In the past few decades, knowledge of OCD has increased, but studies were mostly done in adult population and less studied in children. Although the first study about the prevalence of OCD in children was reported in 1970, there are few population-based studies presented about the prevalence of OCD in children and adolescents recently [32]. The prevalence of OCD in children and adolescents has been reported between 0.5 and 3% [33, 34]. In a recent

It is predicted that OCD is the fourth frequent psychiatric disorder after phobies, substance use disorder, and depression. Studies in different countries and cultures show that OCD prevalence is independent from cultures [27]. Previous epidemiological and clinical studies show that OCD is more frequent among males prior to adolescence and during childhood, the difference between the sexes diminishes to a similar rate as the age advances, and the prevalence rate does not differ between sexes during adolescence and adulthood, and the rates are equal in both sexes at this time [36–46]. Although it was reported in the literature as early as 2 years of age, OCD usually begins at late childhood and early adolescence in youth. Age at onset of the OCD is averagely 10 years old, but age of diagnosis is around 13 years old [47]. Childhoodonset OCD's onset age is approximately 8–11 years old in boys and 11–13 in girls [48].

OCD has adverse effects on family, school, and social lives of children and adolescents [49, 50]. The age of onset has significance in terms of the disease progression. Several studies have detected that OCD often starts at late adolescence and early adulthood period [51, 52].

study, in 16 European countries, median prevalence of OCD was found 0.7% [35].

lation, doing-undoing, reaction formation, and displacement [27].

30 Cognitive Behavioral Therapy and Clinical Applications

**3. Epidemiology**

OCD severity; personal cognitive biases are more relevant in adolescents [28].

It is generally considered that in children obsessive thoughts are less common compared to adults; solely compulsive behaviors in the absence of obsessive thoughts are more frequent, while solely obsessive thinking is less common [45]. However, there are studies in literature showing that all children with compulsive aspect of the disease also have accompanying obsessions [57]. Some studies have reported that unlike adults, children may add their families in their rituals, and they cannot describe triggering factors and stressors as well as adults [42].

According to literature, the most common obsessions among children and adolescents include "fear of contamination, dirt, contracting disease"; "fear of aggressiveness, doing harm-receiving harm"; and "need for symmetry, order and precision", while the most common compulsions are "grooming," "repeating, and checking" [36, 37, 58, 59]. A study including 44 adolescents, 43 early onset adults, and 45 late onset adult OCD patients reported that religious and sexual obsessions are more common in adolescents than in adult patients, obsessions about contamination are more common in adolescents, and grooming compulsions are more frequent in early onset adults than adolescent patients [60]. Onset of OCD is rare before 6 years old. But in cases that began before 6 years old, symptoms usually began with rituals or hand washing and checking [27]. Childhood OCD in boys is 1.5–2 times more than girls [61]. In boys disorder is more severe, and neurological symptoms and comorbidities are more common [27].

Studies that involved children and adolescents diagnosed with OCD reported the frequency of poor insight with the range of 20–45%. Poor insight in children and adolescents with OCD is associated with severity of symptoms and loss of functionality and has a great influence on duration and success of treatment [62, 63]. Poor insight in OCD causes patients not to recognize their symptoms as a problem and results in reduced treatment motivation and treatment success. Therefore OCD patients with poor insight may be misdiagnosed or may not seek treatment [62, 64].
