Patients are randomized to receive either fixed-dose fluoxetine or placebo for 12 weeks. Patients are assessed for psychiatric symptomatology, functional status, and side effects. In addition, to assess attainment of steady state and compliance with treatment, plasma levels of fluoxetine and norfluoxetine are measured at 4, 8, and 12 weeks. To standardize the treatment protocol and to assure that both groups (fluoxetine and placebo) receive equivalent nonpharmacological treatment, a manual is used. Potential predictors of clinical response (such as age, sex, duration and severity of anxiety, school absenteeism, sub-syndromal depressive symptoms, family history of anxiety or mood disorders) are explored.