Inclusion criteria were as follows: (1) Diagnostic and Statistical Manual of Mental Disorders, 4th ed (DSM-IV, American Psychiatric Association 1994) OCD diagnosis as established by standardized interview by a psychiatrist or clinical psychologist using the Structured Clinical Interview for DSM-IV with additional symptom and diagnostic information as previously described (Mattheisen et al. 2015), and (2) onset of obsessions and/or compulsions before age 18.
