title: Primary insomnia: a risk factor to develop depression?
abstract: BACKGROUND
  Chronic insomnia afflicts approximately 5-10% of the adult population in Western industrialized countries. Insomnia may be secondary, i.e. triggered and/or maintained by psychiatric/organic illnesses, the intake of prescribed/illicit drugs or alcohol, or by a combination of these factors. Insomnia can also occur as primary insomnia, caused by a psychophysiological hyperarousal process. In the present review a literature search was undertaken to identify longitudinal epidemiological studies which investigate the question whether primary insomnia at baseline predicts the development of depression at follow-up measurements.
  
  
  METHODS
  MEDLINE search for the medical subject headings insomnia and depression; identification of longitudinal epidemiological studies with at least two measurement points 1 year apart measuring insomnia and depression and indicating explicit criteria for both disorders.
  
  
  RESULTS
  Eight relevant epidemiological studies were identified. Almost unambiguously insomnia at baseline significantly predicted an increased depression risk at follow-up 1-3 years later.
  
  
  CONCLUSIONS
  As insomniac symptoms alone seem to be of predictive value for the development of depression in the succeeding years, it would be worthwhile to investigate if early adequate treatment is able to prevent psychiatric sequelae of primary insomnia.
authors.affiliation: Department of Psychiatry and Psychotherapy, University Hospital of Freiburg, Hauptstrasse 5, 79104 Freiburg, Germany. dieter_riemann@psyallg.ukl.uni-freiburg.de
authors.forename: Dieter
authors.initials: D
authors.lastname: Riemann
authors.forename: Ulrich
authors.initials: U
authors.lastname: Voderholzer
mesh_terms: D000328:Adult; D000368:Aged; D002908:Chronic Disease; D003866:Depressive Disorder / Q000209:etiology* / Q000503:physiopathology; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D007319:Sleep Initiation and Maintenance Disorders / Q000150:complications*