title: The temporal stability and co-morbidity of prolonged fatigue: a longitudinal study in primary care.
abstract: BACKGROUND
  Depression, anxiety and fatigue are among the most common symptoms presented in primary care. Whether such symptoms indicate discrete psychological syndromes or whether they result from a common vulnerability is not clear. This study examined longitudinally the patterns of co-morbidity between prolonged fatigue and other forms of psychological distress in patients attending general practitioners.
  
  
  METHODS
  Adults attending primary care completed questionnaires designed to detect cases of prolonged fatigue and psychological distress at presentation and 12 months later.
  
  
  RESULTS
  Of 652 patients, the prevalence rates of 'prolonged fatigue' alone, 'psychological distress' alone, 'prolonged fatigue + psychological distress' and 'no disorder' were 7%, 19%, 15% and 59% respectively at initial assessment. Of those patients with any prolonged fatigue syndrome initially, 58% still reported fatigue 12 months later (representing 13% of the total sample). Most importantly, the risk of developing prolonged fatigue was not increased in patients who initially had psychological distress (OR = 0.95; 95% CI 0.2-3.6), neither was the risk of developing psychological distress increased in patients who initially had prolonged fatigue (OR = 1.4; 95% CI 0.6-3.4).
  
  
  CONCLUSIONS
  This study indicates that prolonged fatigue is a persistent diagnosis over time. The longitudinal patterns of co-morbidity with psychological distress do not support an aetiological model that proposes a common vulnerability factor for these disorders. Psychiatric classification systems may be better served by treating prolonged fatigue and psychological distress as independent disorders.
authors.affiliation: School of Psychiatry, University of New South Wales, Academic Department of Psychiatry, St George Hospital and Community Health Service, Kogarah, Australia.
authors.forename: I
authors.initials: I
authors.lastname: Hickie
authors.forename: A
authors.initials: A
authors.lastname: Koschera
authors.forename: D
authors.initials: D
authors.lastname: Hadzi-Pavlovic
authors.forename: B
authors.initials: B
authors.lastname: Bennett
authors.forename: A
authors.initials: A
authors.lastname: Lloyd
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001008:Anxiety Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology; D015897:Comorbidity; D003866:Depressive Disorder / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology; D015673:Fatigue Syndrome, Chronic / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009440:Neurasthenia / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology; D009517:New South Wales; D011320:Primary Health Care; D012307:Risk Factors