Admixture analysis of age-of-onset in generalized anxiety disorder

Publication date: Available online 10 May 2017
Source:Journal of Anxiety Disorders
Author(s): Didi Rhebergen, Idan M. Aderka, Ira M. van der Steenstraten, Anton J.L.M. van Balkom, Patricia van Oppen, Max L. Stek, Hannie C. Comijs, Neeltje M. Batelaan
Age-of-onset has been found to be a marker of clinical relevant subtypes in various medical and psychiatric disorders. In addition, clinical importance of age-of-onset has been reported in Generalized Anxiety Disorder (GAD) but in research to date, arbitrary cut-off ages have been used. In this study, admixture analysis was used to determine the best fitting model of age-of-onset distribution in GAD. Data were derived from the Netherlands Study of Depression and Anxiety (NESDA), including 459 participants with a 6-month diagnosis of GAD, aged 18-65 years. The associations between age-of-onset, identified by admixture analysis, and socio-demographics, clinical factors and vulnerability factors were examined using univariate tests and multivariate logistic regression analyses. Two distributions of age-of-onset were identified, with a cut-off age of 24 years. Multivariate analysis showed that early-onset GAD was associated with being female (OR 2.1 (95%CI 1.4-3.2)), higher education (OR 1.1 (95%CI 1.0-1.2)) and higher neuroticism (OR 1.4 (95%CI 1.1-1.7)), while late-onset GAD was associated with somatic illnesses (OR 1.3 (95%CI 1.1-1.7)). Notably, because age-of-onset was assessed retrospectively, recall bias may have been present. In addition, older persons were not included in NESDA, thus we were unable to detect a possible GAD subtype with very-late-onset. To conclude, GAD disorder is characterized by a bimodal age-of-onset, with an objectively determined early age-of-onset cut-off at 24 years. In GAD, early age-of-onset appeared to be of different origin but this did not imply a more severe subtype as compared to older age-of-onset. Future research should use 24 years as the cut-off for early age-of-onset GAD to more accurately determine the clinical relevance of treatment efficacy and course.



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