Epidemiologic studies show that by late adolescence OCD has a lifetime prevalence of 2% to 3%. The age of onset is earlier in boys than in girls, and has a first peak around puberty and another in early adulthood. The natural course of the disorder is fairly stable, with a complete remission rate of 10% to 15%, although fluctuations in symptom level may make short-term apparent outcome unreliable. Comorbid conditions include depression, movement disorders, and anxiety disorders. Although the prevalence of OC symptoms and of OCD are not different for boys and girls, there may be gender differences in the symptom types. The boundary of the diagnosis of OCD is not always easy to determine, and individuals may meet threshold and subthreshold criteria at different times.