title: Psychiatric hospitalizations for affective disorders in Warsaw, Poland: Effect of season and intensity of sunlight.
abstract: The purpose of this study was to assess any associations between the number of hospitalizations for affective disorders, seasons of the year and the intensity of sunlight in Poland, a country with a very changeable climate and significant seasonal fluctuations. We analyzed 2837 admissions with affective disorders hospitalized in the Institute of Psychiatry and Neurology in Warsaw, between 2002 and 2010 (mania, n=380, mixed episode, n=131, bipolar depression, n=736, recurrent depression, n=681, single depressive episode, n=909). For each diagnostic group admission time series were created and categorized into subgroups according to sex and age, and these were analyzed by means of the Autoregressive Integrated Moving Average (ARIMA) method. Regression models and correlations were used to assess the influence of the intensity of sunlight on the number of hospitalizations. Most mania admissions were noted in spring/summer months and in midwinter, mixed episode-late spring and winter, and depression (bipolar, recurrent and single depressive episode)-spring and autumn months. The association between frequency of admissions and monthly hours of sunshine was observed in some age and sex subgroups of patients with bipolar disorder and single depressive episode. The results support the seasonality of admissions of patients with affective disorders.
authors.affiliation: Institute of Psychiatry and Neurology, ul. Sobieskiego 9, 02-957 Warsaw, Poland. Electronic address: mdominia@wp.pl.
authors.forename: Monika
authors.initials: M
authors.lastname: Dominiak
authors.affiliation: Institute of Psychiatry and Neurology, ul. Sobieskiego 9, 02-957 Warsaw, Poland.
authors.forename: Lukasz
authors.initials: L
authors.lastname: Swiecicki
authors.affiliation: Department of Adult Psychiatry, Poznan University of Medical Sciences, ul. Szpitalna 27/33, 60-572 Poznan, Poland.
authors.forename: Janusz
authors.initials: J
authors.lastname: Rybakowski
mesh_terms: D000328:Adult; D000368:Aged; D001714:Bipolar Disorder / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D003863:Depression / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D005260:Female; D006760:Hospitalization / Q000639:trends*; D006778:Hospitals, Psychiatric / Q000639:trends*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019964:Mood Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology*; D011044:Poland / Q000453:epidemiology; D012189:Retrospective Studies; D012621:Seasons; D013472:Sunlight
keywords: Amount of sunlight; Bipolar depression; Hospital admissions; Mania; Recurrent depression; Seasonality