We developed the Toronto Obsessive–Compulsive Scale (TOCS21) to measure widely distributed OC traits in youth and to capture OC dimensions. Each item on the TOCS queries whether a given OC symptom occurs far less often (lower extreme), an average amount of time, or far more often (upper extreme) in the child than in typically developing peers. Questionnaires of this type are designed to generate scores that are widely and more normally distributed in the general population compared with the J-shaped distributions found with typical symptom-based measures (see Supplemental Fig. 1 for TOCS distributions). By including both upper and lower extremes of OC traits, the TOCS can distinguish between the absence of OC symptoms (typically coded as “0” in symptom count-based scales) and the lower extreme.
