**6. Comorbidities**

Among children with OCD, 85% of patients have at least one, and 21–75% have at least two or more additional psychiatric diseases [70–73]. The most commonly reported accompanying diagnoses include anxiety disorder and depression [71, 72, 74]. Several studies involving children and adolescents have reported that attention deficit hyperactivity disorder, Tourette's disorder, oppositional defiant disorder, and generalized anxiety disorder are frequent comorbidities [75–78]. In addition to these accompanying disorders, eating disorders, especially anorexia nervosa, can be frequently observed concurrently with OCD in females [79]. Other studies have found association between early onset OCD and somatoform disorders, tic disorder, impulse control disorder, and high resistance to treatment [80–83].
