Endorsement frequencies and factor structure of DSM-III-R and DSM-IV Generalized Anxiety Disorder symptoms in women: implications for future research, classification, clinical practice and comorbidity.
We investigated dimensions of liability to Generalized Anxiety Disorder (GAD) and whether evidence exists for distinct pathological versus normal clusters in the population. Structured interviews were administered to a general population sample of 2,163 female twins in a cross-sectional design. Endorsement rates were estimated using full information maximum likelihood factor analyses of the DSM-III-R and DSM-IV GAD symptoms, which provides appropriate treatment of the stem-probe structure of the clinical interview. Endorsement rates were highest for symptoms retained in DSM-IV. For both DSM-III-R and DSM-IV, a two-factor model fit the data better than a single-factor model. There was no evidence for non-normality in the liability to GAD. For DSM-III-R, autonomic symptoms loaded on a factor with panic disorder, while fatiguability, difficulty concentrating and hypervigilance loaded on a factor with major depression. For DSM-IV, all items loaded on one factor, and muscle tension also loaded on a second. Major depression, panic, phobias and alcohol dependence diagnoses also loaded on the first factor.


CONCLUSIONS
Future research involving structured interviews should take into account the stem-and-probe format and focus on common factors rather than separate disorders; GAD is not a unidimensional construct and pathological anxiety may differ only quantitatively from normal anxiety.
Kubarych
Thomas S
TS
Department of Psychiatry, Virginia Commonwealth University, Richmond, Virginia 23298-1026, USA. tkubarych@vcu.edu
Aggen
Steven H
SH
Hettema
John M
JM
Kendler
Kenneth S
KS
Neale
Michael C
MC
D000293:Adolescent; D000328:Adult; D001008:Anxiety Disorders / Q000145:classification / Q000175:diagnosis / Q000453:epidemiology; D015897:Comorbidity; D003430:Cross-Sectional Studies; D003866:Depressive Disorder / Q000145:classification / Q000175:diagnosis / Q000453:epidemiology; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008875:Middle Aged; D018433:Twin Studies as Topic