title: DSM-IV psychiatric comorbidity according to symptoms of insomnia: a nationwide sample of Korean adults.
abstract: OBJECTIVE
  The diagnosis of insomnia is based on the presence of four different symptoms: difficulty in initiating sleep (DIS), difficulty in maintaining sleep (DMS), early morning awakening (EMA), and non-restorative sleep (NRS). This study investigated the differences in sociodemographic correlates and psychiatric comorbidity between the four symptoms of insomnia in the general population of South Korea.
  
  
  METHODS
  A sample of the population aged 18-64 (N = 6,510) was questioned using a face-to-face interview. Insomnia was defined as having at least one of the four following symptoms three or more times per week: DIS, DMS, EMA, and NRS. Psychiatric disorders were evaluated using the Korean version of Composite International Diagnostic Interview. Logistic regression analysis was used to test each of the sleep outcomes (DIS, DMS, EMA, or NRS) for an association with sociodemographic and clinical variables.
  
  
  RESULTS
  The prevalence of DIS, DMS, EMA, and NRS were 7.9 % (95 % CI 6.6-9.5 %), 7.9 % (95 % CI 6.5-9.6 %), 4.9 % (95 % CI 3.9-6.0 %), and 14.8 % (95 % CI 12.6-17.4 %), respectively. The overall prevalence of insomnia was 19.0 % (95 % CI 16.1-22.2 %). Being separated, divorced, or widowed, being single, having a part-time job, having a psychiatric illness, and having a physical illness were all significantly related to insomnia. Older age also increased the risk of DMS and EMA, and younger age was a risk factor for NRS. The presence of most psychiatric disorders was significantly related to insomnia. However, the relationship between the psychiatric illness and each insomnia symptom varied and was dependent on the insomnia symptom.
  
  
  CONCLUSIONS
  Most psychiatric disorders were significantly associated with each insomnia symptom in different ways. Differences in sociodemographic and clinical correlates between the four insomnia symptoms implied the heterogeneous characteristics of insomnia as defined by the current diagnostic criteria.
authors.affiliation: Department of Psychiatry, Bucheon Medical Center for the Elderly, Bucheon-si, South Korea.
authors.forename: Byung-Soo
authors.initials: BS
authors.lastname: Kim
authors.forename: Hong Jin
authors.initials: HJ
authors.lastname: Jeon
authors.forename: Jin Pyo
authors.initials: JP
authors.lastname: Hong
authors.forename: Jae Nam
authors.initials: JN
authors.lastname: Bae
authors.forename: Jun-Young
authors.initials: JY
authors.lastname: Lee
authors.forename: Sung Man
authors.initials: SM
authors.lastname: Chang
authors.forename: Young-Moon
authors.initials: YM
authors.lastname: Lee
authors.forename: Jungwoo
authors.initials: J
authors.lastname: Son
authors.forename: Maeng Je
authors.initials: MJ
authors.lastname: Cho
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D044466:Asian People / Q000706:statistics & numerical data; D015897:Comorbidity; D003863:Depression / Q000453:epidemiology* / Q000209:etiology; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012044:Regression Analysis; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D012737:Sex Factors; D007319:Sleep Initiation and Maintenance Disorders / Q000453:epidemiology* / Q000523:psychology; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D055815:Young Adult