title: 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.
abstract: 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.
authors.affiliation: Department of Psychiatry, Virginia Commonwealth University, Richmond, Virginia 23298-1026, USA. tkubarych@vcu.edu
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Kubarych
authors.forename: Steven H
authors.initials: SH
authors.lastname: Aggen
authors.forename: John M
authors.initials: JM
authors.lastname: Hettema
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Kendler
authors.forename: Michael C
authors.initials: MC
authors.lastname: Neale
mesh_terms: 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