Rationale. Obsessive-compulsive disorder (OCD) often has a childhood onset, and is characterized by recurrent obsessions and compulsions that are perceived as irrational and cause significant interference in daily functioning. Neuropsychological and/or neuroimaging investigations have consistently implicated pathways involving the ventral prefrontal cortical regions in the pathophysiology of the disorder. In the absence of attention or memory loss, OCD patients perform more poorly than controls on tasks requiring inhibition of an automatic response. Dysfunction of a frontal-striatal-thalamic circuit in OCD may be mediated by abnormalities in glutamatergic-serotonin neurotransmission, and selective serotonin reuptake inhibitors (SSRIs) are the unique class of psychotropic medication with demonstrated efficacy for youth (and adults) with the disorder.

Objectives and hypotheses. The first objective of the study is to examine how executive functions, metacognition performance, and regional brain activations differ in adolescents with OCD compared to healthy controls. Three specific hypotheses will be tested: (1) in adolescents with OCD, the executive functions related to the frontal cortex will be impaired compared to healthy controls; (2) the metacognition performance of the OCD group will be lower than that of the control group; (3) using fMRI, the OCD group's frontal lobe activations during tasks testing response inhibition and working memory, will be higher than those in the control group. The second objective is to investigate how treatment with the SSRI escitalopram will affect executive functions, metacognition performance, and regional brain activations in adolescents with OCD. After pharmacotherapy, three specific hypotheses will be tested: (1) there will be significant improvement from baseline in the OCD group's frontal executive functions and metacognition performance; (2) the differences on executive functions and metacognition performance between the OCD and control groups will no longer be significant; (3) on repeated fMRI procedures, the OCD group's frontal lobe activations will show a significant decrease from baseline. The third objective is to explore, within the patient group, the relationships between the degree of clinical change, and the magnitude of pre-post-treatment changes in neurocognitive performance, and regional brain activations. The hypothesis is that greater clinical improvement will be associated with greater changes on the selected neurocognitive and neurofunctional measures.

Method. Forty subjects, aged 13-19 years, with a primary DSM-IV diagnosis of OCD, and 40 sex-, and age-matched healthy controls, will be recruited from Ottawa mental health centers and the community. The study will use a pre- post-treatment design, and include three phases. Phase I: Pre-treatment, the OCD subjects will be compared to controls on clinical, neurocognitive, and functional brain activation measures. Phase II: The OCD subjects will receive open treatment with escitalopram (5 mg to 20 mg/day) for 16 weeks. Phase III: The clinical, neurocognitive, and functional brain activations measures will be repeated in all OCD subjects who completed 16 weeks of escitalopram pharmacotherapy, and the neurocognitive measures in control participants after 16 weeks. The Wisconsin Card Sorting Test, Stroop Test, and a Working Memory Task will be used to assess frontal executive functions. The Feeling-of-knowing task and Metacognition Questionnaire will measure metacognition performances. To investigate regional brain activations (only in participants aged 15-19 years), two functional neuroimaging paradigms will be used, a Go/NoGo and a n-Back task, and regional brain activations will be measured using fMRI technology. In patients, clinical severity and changes with treatment will be assessed using the Children's Yale Brown Obsessive-Compulsive Scale, the Maudsley Obsessive-Compulsive Inventory, the State-Trait Anxiety Inventory for Children, and the Children Depression Inventory. Statistical methods will include repeated measures MANOVAS, t-tests, and correlational analyses.