title: Feeling bad in more ways than one: comorbidity patterns of medically unexplained and psychiatric conditions.
abstract: BACKGROUND
  Considerable overlap in symptoms and disease comorbidity has been noted among medically unexplained and psychiatric conditions seen in the primary care setting, such as chronic fatigue syndrome, low back pain, irritable bowel syndrome, chronic tension headache, fibromyalgia, temporomandibular joint disorder, major depression, panic attacks, and posttraumatic stress disorder.
  
  
  OBJECTIVE
  To examine interrelationships among these 9 conditions.
  
  
  METHODS
  Using data from a cross-sectional survey, we described associations and used latent class analysis to investigate complex interrelationships.
  
  
  METHODS
  3,982 twins from the University of Washington Twin Registry.
  
  
  METHODS
  Twins self-reported a doctor's diagnosis of the conditions.
  
  
  RESULTS
  Comorbidity among these 9 conditions far exceeded chance expectations; 31 of 36 associations were significant. Latent class analysis yielded a 4-class solution. Class I (2% prevalence) had high frequencies of each of the 9 conditions. Class II (8% prevalence) had high proportions of multiple psychiatric diagnoses. Class III (17% prevalence) participants reported high proportions of depression, low back pain, and headache. Participants in class IV (73% prevalence) were generally healthy. Class I participants had the poorest markers of health status.
  
  
  CONCLUSIONS
  These results support theories suggesting that medically unexplained conditions share a common etiology. Understanding patterns of comorbidity can help clinicians care for challenging patients.
authors.affiliation: Department of Medicine, University of Washington School of Medicine, Seattle, WA, USA. ellschur@u.washington.edu
authors.forename: Ellen A
authors.initials: EA
authors.lastname: Schur
authors.forename: Niloofar
authors.initials: N
authors.lastname: Afari
authors.forename: Helena
authors.initials: H
authors.lastname: Furberg
authors.forename: Megan
authors.initials: M
authors.lastname: Olarte
authors.forename: Jack
authors.initials: J
authors.lastname: Goldberg
authors.forename: Patrick F
authors.initials: PF
authors.lastname: Sullivan
authors.forename: Dedra
authors.initials: D
authors.lastname: Buchwald
mesh_terms: D000328:Adult; D002908:Chronic Disease / Q000453:epidemiology*; D015897:Comorbidity; D003430:Cross-Sectional Studies; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000453:epidemiology; D004200:Diseases in Twins; D015673:Fatigue Syndrome, Chronic / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D005356:Fibromyalgia / Q000175:diagnosis / Q000453:epidemiology; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000175:diagnosis / Q000453:epidemiology; D017116:Low Back Pain / Q000175:diagnosis / Q000453:epidemiology; D008297:Male; D001523:Mental Disorders / Q000175:diagnosis / Q000453:epidemiology*; D008875:Middle Aged; D016584:Panic Disorder / Q000175:diagnosis / Q000453:epidemiology; D013313:Stress Disorders, Post-Traumatic / Q000175:diagnosis / Q000453:epidemiology; D013705:Temporomandibular Joint Disorders / Q000175:diagnosis / Q000453:epidemiology; D018781:Tension-Type Headache / Q000175:diagnosis / Q000453:epidemiology