title: The structure of depression, anxiety and somatic symptoms in primary care.
abstract: BACKGROUND
  Observed co-morbidity among the mood and anxiety disorders has led to the development of increasingly sophisticated dimensional models to represent the common and unique features of these disorders. Patients often present to primary care settings with a complex mixture of anxiety, depression and somatic symptoms. However, relatively little is known about how somatic symptoms fit into existing dimensional models.
  
  
  METHODS
  We examined the structure of 91 anxiety, depression and somatic symptoms in a sample of 5433 primary care patients drawn from 14 countries. One-, two- and three-factor lower-order models were considered; higher-order and hierarchical variants were studied for the best-fitting lower-order model.
  
  
  RESULTS
  A hierarchical, bifactor model with all symptoms loading simultaneously on a general factor, along with one of three specific anxiety, depression and somatic factors, was the best-fitting model. The general factor accounted for the bulk of symptom variance and was associated with psychosocial dysfunction. Specific depression and somatic symptom factors accounted for meaningful incremental variance in diagnosis and dysfunction, whereas anxiety variance was associated primarily with the general factor.
  
  
  CONCLUSIONS
  The results (a) are consistent with previous studies showing the presence and importance of a broad internalizing or distress factor linking diverse emotional disorders, and (b) extend the bounds of internalizing to include somatic complaints with non-physical etiologies.
authors.affiliation: University at Buffalo, The State University of New York, Buffalo, New York 14221, USA. ljsimms@buffalo.edu
authors.forename: L J
authors.initials: LJ
authors.lastname: Simms
authors.forename: J J
authors.initials: JJ
authors.lastname: Prisciandaro
authors.forename: R F
authors.initials: RF
authors.lastname: Krueger
authors.forename: D P
authors.initials: DP
authors.lastname: Goldberg
mesh_terms: D000339:Affect; D001008:Anxiety Disorders / Q000145:classification / Q000453:epidemiology* / Q000523:psychology; D015897:Comorbidity; D003866:Depressive Disorder / Q000145:classification / Q000453:epidemiology* / Q000523:psychology; D005060:Europe / Q000453:epidemiology; D005163:Factor Analysis, Statistical; D005202:Asia, Eastern / Q000453:epidemiology; D006801:Humans; D007194:India / Q000453:epidemiology; D007389:Internal-External Control; D007406:Interview, Psychological; D008962:Models, Theoretical; D011320:Primary Health Care / Q000706:statistics & numerical data*; D012044:Regression Analysis; D012720:Severity of Illness Index; D013001:Somatoform Disorders / Q000145:classification / Q000453:epidemiology* / Q000523:psychology; D013020:South America / Q000453:epidemiology; D014481:United States / Q000453:epidemiology