a1 Department of Psychiatry and the EMGO Institute for Health and Care Research, VU University Medical Center Amsterdam, The Netherlands
a2 GGZ inGeest, Amsterdam, The Netherlands
a3 Clinical Research Unit for Anxiety and Depression (CRUfAD), University of New South Wales, Sydney, NSW, Australia
a4 Netherlands Institute of Mental Health and Addiction, Utrecht, The Netherlands
a5 Genetic Epidemiological Research Branch, National Institute of Mental Health, Bethesda, MD, USA
Background The nosological status of generalized anxiety disorder (GAD) versus dysthymic disorder (DD) has been questioned. The aim of this study was to examine qualitative differences within (co-morbid) GAD and DD symptomatology.
Method Latent class analysis was applied to anxious and depressive symptomatology of respondents from three population-based studies (2007 Australian National Survey of Mental Health and Wellbeing; National Comorbidity Survey Replication; and Netherlands Mental Health Survey and Incidence Study-2; together known as the Triple study) and respondents from a multi-site naturalistic cohort [Netherlands Study of Depression and Anxiety (NESDA)]. Sociodemographics and clinical characteristics of each class were examined.
Results A three-class (Triple study) and two-class (NESDA) model best fitted the data, reflecting mainly different levels of severity of symptoms. In the Triple study, no division into a predominantly GAD or DD co-morbidity subtype emerged. Likewise, in spite of the presence of pure GAD and DD cases in the NESDA sample, latent class analysis did not identify specific anxiety or depressive profiles in the NESDA study. Next, sociodemographics and clinical characteristics of each class were examined. Classes only differed in levels of severity.
Conclusions The absence of qualitative differences in anxious or depressive symptomatology in empirically derived classes questions the differentiation between GAD and DD.
(Received November 01 2012)
(Revised July 08 2013)
(Accepted July 10 2013)
(Online publication September 11 2013)
† These authors contributed equally to this work.