title: Seasonal variation in suicides and in admissions to hospital for mania and depression.
abstract: BACKGROUND
  The influence of seasons on mood disorders is controversial.
  
  
  OBJECTIVE
  To examine monthly variations in admissions for mania and depressions including variations with sex and age and correlations with frequencies of suicides.
  
  
  METHODS
  All admissions for mania or depression (N=4341) in a population of 1,800,000 with 35,285 admissions in the years 1992-1996 were analysed. All 14,503 suicides in Norway the years 1969-1996 were also analysed.
  
  
  RESULTS
  Admissions for depression had a significant monthly variation for women (chi(2)=29.78, df=11, P<0.005) with the highest peak in November and for men (chi(2)=19.69, df=11, P<0.05) with the highest peak in April. Among women increasing age correlated negatively with the range of monthly observed/expected ratios (r(s)=-0.943, N=6, P<0.01) and with a of maximal monthly observed/expected ratio (r(s)=-0.943, N=6, P<0.01). Among men suicides correlated with admissions for depression (r=0.647, N=12, P<0.05) and mania (r=0.678, N=12, P<0.05).
  
  
  CONCLUSIONS
  The time of admission to hospital are not identical to onset of affective episode. The study was done retrospectively. No sociocultural or physical environmental data were investigated.
  
  
  CONCLUSIONS
  A hypothesis of an influence of seasons on mood disorders is supported. Younger women seem to be especially vulnerable.
authors.affiliation: Østmarka Hospital, Department of Psychiatry and Behavioural Medicine, The Medical Faculty, The Norwegian University of Science and Technology, Trondheim, Norway. gunnar.morken@medisin.ntnu.no
authors.forename: Gunnar
authors.initials: G
authors.lastname: Morken
authors.forename: Solfrid
authors.initials: S
authors.lastname: Lilleeng
authors.forename: Olav M
authors.initials: OM
authors.lastname: Linaker
mesh_terms: D001714:Bipolar Disorder / Q000453:epidemiology*; D003866:Depressive Disorder / Q000453:epidemiology*; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D009664:Norway / Q000453:epidemiology; D012621:Seasons; D012737:Sex Factors; D013405:Suicide