title: Seasonal BMI differences between restrictive and purging anorexia nervosa subtypes.
abstract: OBJECTIVE
  Seasonal differences in anorexia nervosa is an area of research which has received scarce attention in the literature. The aim of this study was to explore patterns of seasonal variation in body weight in anorexia nervosa patients admitted to an eating disorders unit from January 2007 to December 2011.
  
  
  METHODS
  Anorexia nervosa restrictive (ANR) and binge eating/purging (ANBP) subtypes were compared with respect to BMI on admission during the Warm and Cold Semester, and in terms of lenght of hospital stay.
  
  
  RESULTS
  The main result was that BMI differences between ANBP and ANR patients were due to bodyweight differences during the colder months of the year (p < 0.01) whereas no difference in bodyweight on admission was observed between both subtypes during the Warm Semester months. Furthermore, ANR patients' bodyweight was lower when admitted during the Cold compared to the Warm Semester (p < 0.05). Length of stay was significantly associated with reduced BMI in ANR patients (p < 0.01), but not so for ANBP patients.
  
  
  CONCLUSIONS
  To our knowledge, this is the first study in the literature providing data on seasonal variations in the BMI on admission of anorexia nervosa patients, and in the length of hospitalization.
authors.affiliation: Departamento de Psicología Clínica y Psicobiología, Facultad de Psicología, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
authors.forename: Angela
authors.initials: A
authors.lastname: Fraga
authors.forename: Veronica
authors.initials: V
authors.lastname: Caggianesse
authors.forename: Olaia
authors.initials: O
authors.lastname: Carrera
authors.forename: Montserrat
authors.initials: M
authors.lastname: Graell
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Morandé
authors.forename: Emilio
authors.initials: E
authors.lastname: Gutiérrez
mesh_terms: D000293:Adolescent; D000856:Anorexia Nervosa / Q000145:classification / Q000150:complications / Q000503:physiopathology*; D015992:Body Mass Index; D052018:Bulimia Nervosa / Q000150:complications / Q000503:physiopathology; D005260:Female; D006760:Hospitalization; D006801:Humans; D007902:Length of Stay; D012621:Seasons
keywords: ambient temperature; binge eating-purging anorexia; restrictive anorexia; seasonality