A family study of early-onset obsessive-compulsive disorder

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Abstract
Results from family studies have suggested that obsessive‐compulsive disorder (OCD) is a genetically heterogeneous disorder and have emphasized the importance of identifying valid subgroups of patients. The current study focused on early‐onset OCD probands and examined the recurrence risks of OCD and tics among first‐degree family members. One hundred six children and adolescents with OCD were recruited from a specialty clinic for OCD and 44 control individuals without OCD were identified by random‐digit dialing. These 150 probands and their 465 first‐degree relatives were assessed by trained interviewers, using standardized semi‐structured interviews. Diagnoses were assigned according to DSM‐IV criteria by two experts blind to the proband's diagnosis, through the best‐estimate process. These data were analyzed using χ2 tests, t‐tests, logistic regression, and generalized estimating equations (GEE). Case probands had a mean age of onset of OC symptoms of 6.7 years (SD = 2.8), and high comorbid rates with Tourette syndrome (33%) and chronic tics (13.2%). Compared to control relatives, case relatives had higher age‐corrected recurrence risks of OCD (22.7% vs. 0.9%, odds ratio (OR) = 32.5, 95% confidence interval (CI) = 4.5–230.8, P = 0.0005), and chronic tics (11.6% vs. 1.7%, OR = 7.9, 95% CI = 1.9–33.1, P = 0.005). A comorbid diagnosis of tics in the relatives was the best predictor of their diagnosis of OCD (OR = 7.35, 95% CI = 3.79–14.25, P < 0.0001). There was a significant correlation between the ages of onset of OCD in probands and their affected relatives. Childhood onset OCD is a highly familial disorder. Some early‐onset cases may represent a valid subgroup, with higher genetic loading and shared vulnerability with chronic tic disorders.