(sum of all 21 items; range: − 63 to 63) was significantly associated with age, gender and respondent (p < 0.05), we created standardized TOCS z scores. Total scores were modeled using linear regression controlling for age and gender, for parent- and self-respondents separately and residual scores were obtained. Participants were divided into 30 groups according to respondent (parent- or self-report), gender, and integer age. Parent-report groups included integer ages from 6 to 15 and self-report groups included integer ages from 13 to 17. Standardized scores corresponding to the empirical percentile of each individual were assigned within each of the 30 groups separately. We compared the heritability of the TOCS total score to an established measure of OC symptoms: the CBCL-OCS22,23. Each of the eight CBCL-OCS items were scored on a scale of 0–2 (0 = not true; 1 = somewhat/sometimes true; and 2 = very/often true), and were summed to generate a total score (range: 0–16).
