title: Seasonal spring peaks of suicide in victims with and without prior history of hospitalization for mood disorders.
abstract: BACKGROUND
  Seasonal spring peaks of suicide are highly replicated, but their origin is poorly understood. As the peak of suicide in spring could be a consequence of decompensation of mood disorders in spring, we hypothesized that prior history of mood disorders is predictively associated with suicide in spring.
  
  
  METHODS
  We analyzed the monthly rates of suicide based upon all 37,987 suicide cases in the Danish Cause of Death Registry from 1970 to 2001. History of mood disorder was obtained from the Danish Psychiatric Central Register and socioeconomical data from the Integrated Database for Labour Market Research. The monthly rate ratio of suicide relative to December was estimated using a Poisson regression. Seasonality of suicide between individuals with versus without hospitalization for mood disorders was compared using conditional logistic regression analyses with adjustment for income, marital status, place of residence, and method of suicide.
  
  
  RESULTS
  A statistically significant spring peak in suicide was observed in both groups. A history of mood disorders was associated with an increased risk of suicide in spring (for males: RR=1.18, 95% CI 1.07-1.31; for females: RR=1.20, 95% CI 1.10-1.32).
  
  
  CONCLUSIONS
  History of axis II disorders was not analyzed. Danish socioeconomical realities have only limited generalizability.
  
  
  CONCLUSIONS
  The results support the need to further investigate if exacerbation of mood disorders in spring triggers seasonal peaks of suicide. Identifying triggers for seasonal spring peaks in suicide may lead to uncovering novel risk factors and therapeutic targets for suicide prevention.
authors.affiliation: Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD 21201, USA. tpostola@psych.umaryland.edu
authors.forename: Teodor T
authors.initials: TT
authors.lastname: Postolache
authors.forename: Preben B
authors.initials: PB
authors.lastname: Mortensen
authors.forename: Leonardo H
authors.initials: LH
authors.lastname: Tonelli
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Jiao
authors.forename: Constantin
authors.initials: C
authors.lastname: Frangakis
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Soriano
authors.forename: Ping
authors.initials: P
authors.lastname: Qin
mesh_terms: D000328:Adult; D001714:Bipolar Disorder / Q000175:diagnosis / Q000401:mortality* / Q000523:psychology; D002423:Cause of Death; D003430:Cross-Sectional Studies; D003718:Denmark; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000401:mortality* / Q000523:psychology; D018450:Disease Progression; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010359:Patient Readmission / Q000706:statistics & numerical data*; D016012:Poisson Distribution; D012008:Recurrence; D012042:Registries; D012306:Risk; D012621:Seasons; D012959:Socioeconomic Factors; D013405:Suicide / Q000523:psychology* / Q000706:statistics & numerical data*; D014754:Violence / Q000523:psychology / Q000706:statistics & numerical data