Table 2. Incidence Risk Ratio of Obsessive-Compulsive Disorder in Relation to Individual and Parental Diagnoses of Autism Spectrum Disorders (ASD; 1994–2012).

	Risk of Obsessive-Compulsive Disorder
Diagnosis of Autism Spectrum Disorder	Incidence Rate Ratio	95% CI
Parental Diagnosis of Autism	3.08	0.96–7.16
Individidual Diagnosis of Autism	2.51	2.20–2.84
Individidual Diagnosis of Childhood Autism	1.39	0.98–1.91
Individidual Diagnosis of Atypical Autism	0.63	0.16–1.65
Individidual Diagnosis of Asperger's Syndrome	3.05	2.49–3.69
Individidual Diagnosis of Other Pervasive Developmental Disorder	1.99	1.40–2.71
Individidual Diagnosis of Unspecified Pervasive Developmental Disorder	3.5	2.80–4.32

Estimates of relative risk were adjusted for calendar year, age, maternal and paternal age, sex, parental history of psychiatric illness, first psychiatric hospital contact for any other disorder, place of residence at time of birth and the interaction of age with sex