title: Seasonality in depressive and anxiety symptoms among primary care patients and in patients with depressive and anxiety disorders; results from the Netherlands Study of Depression and Anxiety.
abstract: BACKGROUND
  Little is known about seasonality of specific depressive symptoms and anxiety symptoms in different patient populations. This study aims to assess seasonal variation of depressive and anxiety symptoms in a primary care population and across participants who were classified in diagnostic groups 1) healthy controls 2) patients with a major depressive disorder, 3) patients with any anxiety disorder and 4) patients with a major depression and any anxiety disorder.
  
  
  METHODS
  Data were used from the Netherlands Study of Depression and Anxiety (NESDA). First, in 5549 patients from the NESDA primary care recruitment population the Kessler-10 screening questionnaire was used and data were analyzed across season in a multilevel linear model. Second, in 1090 subjects classified into four groups according to psychiatric status according to the Composite International Diagnostic Interview, overall depressive symptoms and atypical versus melancholic features were assessed with the Inventory of Depressive Symptoms. Anxiety and fear were assessed with the Beck Anxiety Inventory and the Fear questionnaire. Symptom levels across season were analyzed in a linear regression model.
  
  
  RESULTS
  In the primary care population the severity of depressive and anxiety symptoms did not show a seasonal pattern. In the diagnostic groups healthy controls and patients with any anxiety disorder, but not patients with a major depressive disorder, showed a small rise in depressive symptoms in winter. Atypical and melancholic symptoms were both elevated in winter. No seasonal pattern for anxiety symptoms was found. There was a small gender related seasonal effect for fear symptoms.
  
  
  CONCLUSIONS
  Seasonal differences in severity or type of depressive and anxiety symptoms, as measured with a general screening instrument and symptom questionnaires, were absent or small in effect size in a primary care population and in patient populations with a major depressive disorder and anxiety disorders.
authors.affiliation: Department of Psychiatry, University Medical Centre Groningen, University of Groningen, The Netherlands. w.h.winthorst@umcg.nl
authors.forename: Wim H
authors.initials: WH
authors.lastname: Winthorst
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Post
authors.forename: Ybe
authors.initials: Y
authors.lastname: Meesters
authors.forename: Brenda W H J
authors.initials: BW
authors.lastname: Penninx
authors.forename: Willem A
authors.initials: WA
authors.lastname: Nolen
mesh_terms: D000293:Adolescent; D000328:Adult; D001008:Anxiety Disorders / Q000175:diagnosis / Q000453:epidemiology*; D016022:Case-Control Studies; D003866:Depressive Disorder / Q000175:diagnosis / Q000453:epidemiology*; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D011320:Primary Health Care / Q000706:statistics & numerical data*; D011569:Psychiatric Status Rating Scales; D012044:Regression Analysis; D012621:Seasons; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires