Age at onset in Canadian OCD patients: mixture analysis and systematic comparison with other studies.

OBJECTIVE

This study aimed to determine the distributions of the age at onset (AAO) using mixture analysis and better develop the understanding of AAO as a clinical feature of obsessive-compulsive disorder.

METHOD

Mixture analysis was used to identify sub-groups characterized by differences in AAO. Clinical features were analyzed for differences in AAO sub-groups using mixture analysis. Comparisons were made with AAO cut-offs used in previous studies using the 2-Sample Kolmogorov-Smirnov Test.

RESULTS

Mixture analysis of our sample (n=196) yielded a combination of 2 normal theoretical distributions with means (SD) of 9.66 (3.12) for the early-onset sub-group and 21.1 (8.36) years for the late-onset sub-group. The sub-groups were divided by a cut-off of 15 years. As expected, a negative correlation was found between AAO and duration of illness. The early-onset subjects had significantly lower age at the time of the assessment and they tended to have more often panic attacks but were treated less often with benzodiazepines and other anti-anxiety medications. The comparison analysis showed significant difference in the AAO distribution between our sample and four other study samples.

CONCLUSIONS

Our findings support the notion that different AAO sub-groups correspond with differences in clinical presentations of obsessive-compulsive disorder.