**5. Etiology**

OCD pathogenesis involves neuroanatomy, biochemical, genetic, and environmental factors. Brain structures that are associated with obsessive compulsive disorder include the orbitofrontal cortex, striatum, thalamus, and the basal ganglia, which are all involved in the cortical-striatal circuit [38]. MRI and fMRI scans have demonstrated structural abnormalities for individuals with OCD. Biochemical factors that have been identified to play a role include neurotransmitters like serotonin [38, 39], and in fact, serotonin changes have been shown to change purely with an intensive exposure and response prevention treatment [40]. Genetic factors also appear to have a strong influence on the development of early-onset OCD. Children with OCD are likely to have other first-degree relatives that also have OCD as well as anxiety, mood, ADHD, and tic disorders [9]. Numerous studies have demonstrated elevated rates of OCD in parents of children with early onset of the disorder, including a study that found a quarter of fathers and almost 10% of mothers meeting criteria for OCD [41]. For a subset of individuals, the pathogenesis of OCD is related to an autoimmune infectious disease known as autoimmune neuropsychiatric disorders associated with Streptococcus (PANDAS), which is also implicated in Tourette's disorder. It has been suggested this year that PANDAS be renamed to encephalitis autoimmune disorder poststreptococci.

With regard to environmental factors, family environment has been identified as a likely contributor to OCD development in children [42]. Social learning is theorized to play an important role in the development of childhood anxiety disorders. Children learn from seeing how their parents function in the world and how their parents cope with their own anxiety and emotional distress. Additionally, parent communication style and relationship quality impacts child development of psychopathology. Authoritarian parenting style (low warmth, high behavioral control) has been linked to higher incidences of obsessive compulsive symptoms and obsessive compulsive beliefs (such as regarding the importance of thoughts and personal responsibility) [43]. This finding is consistent with other studies that have demonstrated an association between parental control and higher rates of child anxiety [44]. Family factors are therefore important to address in the treatment of pediatric OCD.
