Psychological Medicine

The effects of co-morbidity on the onset and persistence of generalized anxiety disorder in the ICPE surveys 1

R. C.  KESSLER  a1 c1, L. H.  ANDRADE  a1, R. V.  BIJL  a1, D. R.  OFFORD  a1, O. V.  DEMLER  a1 and D. J.  STEIN  a1
a1 Department of Health Care Policy, Harvard Medical School, Boston, MA, USA; Department of Psychiatry, LIM-23, School of Medicine, University of São Paulo, São Paulo, Brazil; The Netherlands Institute of Mental Health and Addictions, Utrecht, The Netherlands; Department of Psychiatry, McMaster University, Hamilton, Ontario, Canada; and Medical Research Council Unit on Anxiety Disorders, Department of Psychiatry, University of Stellenbosch, Cape Town, South Africa


Background. Although it is well known that generalized anxiety disorder (GAD) is highly co-morbid with other mental disorders, little is known about the extent to which earlier disorders predict the subsequent first onset and persistence of GAD. These associations are examined in the current report using data from four community surveys in the World Health Organization (WHO) International Consortium in Psychiatric Epidemiology (ICPE).

Method. The surveys come from Brazil, Canada, the Netherlands and the United States. The Composite International Diagnostic Interview (CIDI) was used to assess DSM-III-R anxiety, mood and substance use disorders in these surveys. Discrete-time survival analysis was used to examine the associations of retrospectively reported earlier disorders with first onset of GAD. Logistic regression analysis was used to examine the associations of the disorders with persistence of GAD.

Results. Six disorders predict first onset of GAD in all four surveys: agoraphobia, panic disorder, simple phobia, dysthymia, major depression and mania. With the exception of simple phobia, only respondents with active disorders have elevated risk of GAD. In the case of simple phobia, in comparison, respondents with a history of remitted disorder also have consistently elevated risk of GAD. Simple phobia is also the only disorder that predicts the persistence of GAD.

Conclusions. The causal processes linking temporally primary disorders to onset of GAD are likely to be state-dependent. History of simple phobia might be a GAD risk marker. Further research is needed to explore the mechanisms involved in the relationship between simple phobia and subsequent GAD.

c1 Address for correspondence: Dr Ronald C. Kessler, Department of Health Care Policy, Harvard Medical School, 180 Longwood Avenue, Boston, MA 02115-5899, USA.


1 More information on the International Consortium in Psychiatric Epidemiology (ICPE) may be obtained from the