title: Seasonal variation of depressive symptoms in unipolar major depressive disorder.
abstract: OBJECTIVE
  Retrospective and cross-sectional studies of seasonal variation of depressive symptoms in unipolar major depression have yielded conflicting results. We examined seasonal variation of mood symptoms in a long-term prospective cohort - the Collaborative Depression Study (CDS).
  
  
  METHODS
  The sample included 298 CDS participants from five academic centers with a prospectively derived diagnosis of unipolar major depression who were followed for at least ten years of annual or semi-annual assessments. Generalized linear mixed models were utilized to investigate the presence of seasonal patterns. In a subset of 271 participants followed for at least 20 years, the stability of a winter depressive pattern was assessed across the first two decades of follow-up.
  
  
  RESULTS
  A small increase in proportion of time depressed was found in the months surrounding the winter solstice, although the greatest symptom burden was seen in December through April with a peak in March. The relative burden of winter depressive symptoms in the first decade demonstrated no relationship to that of the second decade. The onset of new episodes was highest October through January, peaking in January.
  
  
  CONCLUSIONS
  There exists a small but statistically significant peak in depressive symptoms from the month of the winter solstice to the month of the spring equinox. However, the predominance of winter depressive symptoms did not appear stable over the long-term course of illness.
authors.affiliation: Carver College of Medicine, College of Public Health, The University of Iowa, Iowa City, IA.
authors.forename: Bryan S
authors.initials: BS
authors.lastname: Cobb
authors.affiliation: Department of Psychiatry, College of Public Health, The University of Iowa, Iowa City, IA.
authors.forename: William H
authors.initials: WH
authors.lastname: Coryell
authors.affiliation: Department of Biostatistics, College of Public Health, The University of Iowa, Iowa City, IA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Cavanaugh
authors.affiliation: Department of Psychiatry and Human Behavior, The Warren Alpert Medical School of Brown University, Providence, RI, 02912.
authors.forename: Martin
authors.initials: M
authors.lastname: Keller
authors.affiliation: Department of Psychiatry and Human Behavior, The Warren Alpert Medical School of Brown University, Providence, RI, 02912; UpToDate Inc., Waltham, MA.
authors.forename: David A
authors.initials: DA
authors.lastname: Solomon
authors.affiliation: Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY; New York State Psychiatric Institute, New York, NY.
authors.forename: Jean
authors.initials: J
authors.lastname: Endicott
authors.affiliation: Department of Psychiatry, College of Public Health, The University of Iowa, Iowa City, IA.
authors.forename: James B
authors.initials: JB
authors.lastname: Potash
authors.affiliation: Department of Psychiatry, College of Public Health, The University of Iowa, Iowa City, IA; Department of Internal Medicine, College of Public Health, The University of Iowa, Iowa City, IA; Department of Epidemiology, College of Public Health, The University of Iowa, Iowa City, IA. Electronic address: jess-fiedorowicz@uiowa.edu.
authors.forename: Jess G
authors.initials: JG
authors.lastname: Fiedorowicz
mesh_terms: D000328:Adult; D003865:Major Depressive Disorder / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010507:Periodicity; D012621:Seasons