A computerized, English questionnaire covered demographics, medical history, and two measures of OC traits and symptoms. The TOCS had 21 items scored on a scale of − 3 to + 3 (− 3 = far less often than average; − 2 = less often than average; − 1 = slightly less often than average; 0 = average amount of time; 1 = slightly more often than average; 2 = more often than average; and 3 = far more often than average). The TOCS has been shown to have high internal consistency (Cronbach’s σ = 0.94) and to discriminate between an OCD measure (the Obsessive–Compulsive Scale of the Child Behavior Checklist (CBCL-OCS22,23) Spearman correlation = 0.5) and an ADHD measure (the Strengths and Weaknesses of ADHD Symptoms and Normal Behavior scale (SWAN24), Spearman’s correlation = 0.02)21. Because the TOCS total score (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
