title: Longitudinal course of depression scores with and without insomnia in non-depressed individuals: a 6-year follow-up longitudinal study in a Korean cohort.
abstract: OBJECTIVE
  This is a population-based longitudinal study that followed insomnia symptoms over a 6-year period in non-depressed individuals. The purpose of the study was to (1) investigate the longitudinal course of depression based on number of insomnia episodes; and (2) describe longitudinal associations between insomnia and depression, and insomnia and suicidal ideation.
  
  
  METHODS
  Population-based longitudinal study.
  
  
  METHODS
  Community-based sample from the Korean Genome and Epidemiology Study (KoGES).
  
  
  METHODS
  1,282 non-depressed individuals (44% male, mean age 52.3 ± 7.14 years).
  
  
  RESULTS
  This study prospectively assessed insomnia, depression, and suicidal ideation with 4 time points. Individuals were classified into no insomnia (NI), single episode insomnia (SEI), and persistent insomnia (PI; ≥ insomnia at 2+ time points) groups based on number of times insomnia was indicated. Mixed effects modeling indicated that depression scores increased significantly faster in the PI group compared to the NI (P < 0.001) and SEI (P = 0.02) groups. Additionally, the PI group had significantly increased odds of depression as compared to NI or SEI (OR 2.44, P = 0.001) groups, with 18.7% meeting criteria for depression compared to the NI (5.3%) and SEI (11.6%) groups at end point. The PI group also had significantly increased odds of suicidal ideation as compared to NI or SEI (OR 1.86, P = 0.002) groups.
  
  
  CONCLUSIONS
  Persistent insomnia significantly increases the rate in which depression occurs over time in non-depressed individuals, which ultimately leads to higher risk for depression. Additionally, having persistent insomnia also increased the risk of suicidal ideation.
  
  
  BACKGROUND
  Suh S; Kim H; Yang HC; Cho ER; Lee SK; Shin C. Longitudinal course of depression scores with and without insomnia in non-depressed individuals: a 6-year follow-up longitudinal study in a Korean cohort. SLEEP 2013;36(3):369-376.
authors: Korea University Ansan Medical Center, Institute of Human Genomic Study, Ansan, Republic of Korea.
authors: Sooyeon
authors: S
authors: Suh
authors: Hyun
authors: H
authors: Kim
authors: Hae-Chung
authors: HC
authors: Yang
authors: Eo Rin
authors: ER
authors: Cho
authors: Seung Ku
authors: SK
authors: Lee
authors: Chol
authors: C
authors: Shin
mesh_terms: D015331:Cohort Studies; D015897:Comorbidity; D003866:Depressive Disorder / Q000453:epidemiology* / Q000523:psychology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007723:Korea / Q000453:epidemiology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011446:Prospective Studies; D012307:Risk Factors; D007319:Sleep Initiation and Maintenance Disorders / Q000453:epidemiology* / Q000523:psychology; D059020:Suicidal Ideation
keywords: Insomnia; depression; epidemiology; mental health; suicidal ideation