Feeling Bad in More Ways than One: Comorbidity Patterns of Medically Unexplained and Psychiatric Conditions

  • Ellen A. SchurEmail author
  • Niloofar Afari
  • Helena Furberg
  • Megan Olarte
  • Jack Goldberg
  • Patrick F. Sullivan
  • Dedra Buchwald
Original Article



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.


To examine interrelationships among these 9 conditions.


Using data from a cross-sectional survey, we described associations and used latent class analysis to investigate complex interrelationships.


3,982 twins from the University of Washington Twin Registry.


Twins self-reported a doctor’s diagnosis of the conditions.


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.


These results support theories suggesting that medically unexplained conditions share a common etiology. Understanding patterns of comorbidity can help clinicians care for challenging patients.


primary care fibromyalgia chronic fatigue syndrome back pain depression 



This research was supported by National Institutes of Health awards 5 U19 AI038429 (Buchwald) and R55AR051524 (Afari). Dr. Schur is funded by a National Institutes of Health Career Development Award K23 DK070826.

Conflict of Interest

None disclosed.


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Copyright information

© Society of General Internal Medicine 2007

Authors and Affiliations

  • Ellen A. Schur
    • 1
    • 5
    Email author
  • Niloofar Afari
    • 2
  • Helena Furberg
    • 3
  • Megan Olarte
    • 3
  • Jack Goldberg
    • 4
  • Patrick F. Sullivan
    • 3
  • Dedra Buchwald
    • 1
  1. 1.Department of MedicineUniversity of Washington School of MedicineSeattleUSA
  2. 2.Department of PsychiatryUniversity of California, San Diego & VA San Diego Healthcare SystemSan DiegoUSA
  3. 3.Department of GeneticsUniversity of North Carolina at Chapel HillChapel HillUSA
  4. 4.Department of EpidemiologyUniversity of Washington & Vietnam Era Twin RegistrySeattleUSA
  5. 5.Harborview Medical CenterSeattleUSA

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