title: Prevalence, course, and comorbidity of insomnia and depression in young adults.
abstract: OBJECTIVE
  (1) To describe the prevalence and prospective course of insomnia in a representative young-adult sample and (2) to describe the cross-sectional and longitudinal associations between insomnia and depression.
  
  
  METHODS
  Longitudinal cohort study.
  
  
  METHODS
  Community of Zurich, Switzerland.
  
  
  METHODS
  Representative stratified population sample.
  
  
  METHODS
  None.
  
  
  RESULTS
  The Zurich Study prospectively assessed psychiatric, physical, and sleep symptoms in a community sample of young adults (n=591) with 6 interviews spanning 20 years. We distinguished 4 duration-based subtypes of insomnia: 1-month insomnia associated with significant distress, 2- to 3-week insomnia, recurrent brief insomnia, and occasional brief insomnia. The annual prevalence of 1-month insomnia increased gradually over time, with a cumulative prevalence rate of 20% and a greater than 2-fold risk among women. In 40% of subjects, insomnia developed into more chronic forms over time. Insomnia either with or without comorbid depression was highly stable over time. Insomnia lasting 2 weeks or longer predicted major depressive episodes and major depressive disorder at subsequent interviews; 17% to 50% of subjects with insomnia lasting 2 weeks or longer developed a major depressive episode in a later interview. "Pure" insomnia and "pure" depression were not longitudinally related to each other, whereas insomnia comorbid with depression was longitudinally related to both.
  
  
  CONCLUSIONS
  This longitudinal study confirms the persistent nature of insomnia and the increased risk of subsequent depression among individuals with insomnia. The data support a spectrum of insomnia (defined by duration and frequency) comorbid with, rather than secondary to, depression.
authors.affiliation: Department ofPsychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA. buyssedj@upmc.edu
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Buysse
authors.forename: Jules
authors.initials: J
authors.lastname: Angst
authors.forename: Alex
authors.initials: A
authors.lastname: Gamma
authors.forename: Vladeta
authors.initials: V
authors.lastname: Ajdacic
authors.forename: Dominique
authors.initials: D
authors.lastname: Eich
authors.forename: Wulf
authors.initials: W
authors.lastname: Rössler
mesh_terms: D000328:Adult; D002908:Chronic Disease; D015331:Cohort Studies; D015897:Comorbidity; D003430:Cross-Sectional Studies; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology; D039721:Diagnostic and Statistical Manual of Mental Disorders; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D010507:Periodicity; D015995:Prevalence; D011446:Prospective Studies; D012720:Severity of Illness Index; D007319:Sleep Initiation and Maintenance Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology; D013997:Time Factors