title: Infection load as a predisposing factor for somatoform disorders: evidence from a Dutch General Practice Registry.
abstract: OBJECTIVE
  Somatoform disorders (SDs) are characterized by chronic multiple functional somatic (FS) symptoms. It has been suggested that infections may be triggers for FS symptoms to occur, pointing to the immune system as a pathogenic factor in their development. The current study aimed to compare the prevalence of infections (i.e., infection load) in the history of patients with SDs with that of matched controls.
  
  
  METHODS
  Samples (n = 185) were identified in the Psychiatric Case Register Middle Netherlands and the Julius General Practitioners Network. Patients with an SD diagnosis in the Psychiatric Case Register Middle Netherlands were compared with matched persons without somatoform complaints (controls) on their infection load in two periods before the date of the psychiatric diagnosis or a matched date for the controls (i.e., the total period for which data were available and a 3-year period). Infection load was defined as the total number of infections documented in the Julius General Practitioners Network.
  
  
  RESULTS
  Patients with SD had significantly more infections than did controls in both periods (total period: mean [standard error] = 0.87 [0.10] versus 0.51 [0.06], z = -3.08, p = .002; 3-year period: 3.44 [0.47] versus 2.15 [0.50], z = -2.91, p = .004).
  
  
  CONCLUSIONS
  Results show that patients with SD have a higher infection load preceding their diagnosis as compared with matched controls, implicating that infection load may indeed predispose for developing FS symptoms. These findings emphasize the importance of further research on immunological mechanisms in FS symptoms. Limitations of the study are discussed.
authors: Clinical and Health Psychology, Research Institute of Social and Behavioral Sciences, Utrecht University, T.E. Lacourt, Heidelberglaan 1, 3584 CS, Utrecht, the Netherlands. T.E.Lacourt@uu.nl.
authors: Tamara E
authors: TE
authors: Lacourt
authors: Jan H
authors: JH
authors: Houtveen
authors: Hugo M
authors: HM
authors: Smeets
authors: Myriam M
authors: MM
authors: Lipovsky
authors: Lorenz J P
authors: LJ
authors: van Doornen
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D003141:Communicable Diseases / Q000453:epidemiology*; D004198:Disease Susceptibility; D005194:Family Practice / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D009426:Netherlands / Q000453:epidemiology; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data; D015995:Prevalence; D012042:Registries; D013001:Somatoform Disorders / Q000175:diagnosis / Q000453:epidemiology*; D013315:Stress, Psychological / Q000453:epidemiology*
keywords: functional somatic symptoms; infection; inflammation; somatoform disorder