title: Seasonal variation in affective and other clinical symptoms among high-risk families for bipolar disorders in an Arctic population.
abstract: BACKGROUND
  In bipolar disorder (BD), seasonality of symptoms is common and disturbances in circadian rhythms have been reported.
  
  
  OBJECTIVE
  We identified high-penetrance families in a geographically restricted area in Northern Fennoscandia and studied the seasonal variation of clinical symptoms among BD subjects and their healthy relatives.
  
  
  METHODS
  We explored the clinical characteristics of subjects living in Northern Fennoscandia, with extreme annual variation in daylight. Among known indigenous high-risk families for BD, we compared the affected ones (N=16) with their healthy relatives (N=15), and also included 18 healthy non-related controls from the same geographical area. Seasonal fluctuation in clinical measures was followed up at the 4 most demarcated photoperiodic time points of the annual cycle: around the summer solstice and autumn equinox in 2013, the winter solstice in 2013/2014, and the spring equinox in 2014. In the baseline, lifetime manic symptoms [Mood Disorder Questionnaire (MDQ)] and morningness-eveningness questionnaire type (MEQ) were registered, whereas in the follow-up, depressive [Beck Depression Inventory (BDI)] and distress [General Health Questionnaire (GHQ-12)] symptoms and alcohol consumption and sleep were recorded.
  
  
  RESULTS
  Possibly indicative or statistically significant differences in symptoms between the affected subjects and their healthy relatives were the BDI winter (13.3 vs. 2.6, t=-2.51, p=0.022) and spring scores (12.6 vs. 3.2, t=-1.97, p=0.063) and GHQ winter (4.2 vs. 0.82, t=-2.08, p=0.052) and spring scores (3.8 vs. 0.82, t=-1.97, p=0.063). Scores were higher among the affected subjects, exceeding a possibly diagnostic threshold (10 and 3) at all the time points, and without the notable seasonality which was observed among the healthy relatives. In the overall population, MDQ and MEQ scores had an inverse correlation (-0.384, significant at 0.016), indicating increased lifetime manic behaviour among "the night owl" chronotype subjects.
  
  
  CONCLUSIONS
  In an Arctic population sample, we found different seasonal fluctuation in mood and distress symptoms and sleep duration scores between subjects with bipolar spectrum disorders and their healthy relatives. Despite the relatively small sample size, the results indicate that the symptoms and signs of BD relate to a disturbance in seasonal variation. Seasonal variation can be considered as an interesting endophenotype for BD and a promising target for further genetic studies.
authors.affiliation: Department of Psychiatry, University and University Hospital of Oulu, Oulu, Finland.|National Institute of Health and Welfare, Helsinki, Finland.|Depertment of Social Psychiatry, School of Health Sciences, University of Tampere, Tampere, Finland; sami.pirkola@uta.fi.
authors.forename: Sami
authors.initials: S
authors.lastname: Pirkola
authors.affiliation: Centre of Arctic Medicine, Thule Institute, University of Oulu, Oulu, Finland.
authors.forename: Heidi A
authors.initials: HA
authors.lastname: Eriksen
authors.affiliation: National Institute of Health and Welfare, Helsinki, Finland.
authors.forename: Timo
authors.initials: T
authors.lastname: Partonen
authors.affiliation: Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland.
authors.forename: Tuula
authors.initials: T
authors.lastname: Kieseppä
authors.affiliation: Department of Psychiatry, University and University Hospital of Oulu, Oulu, Finland.
authors.forename: Juha
authors.initials: J
authors.lastname: Veijola
authors.affiliation: Department of Psychiatry, University and University Hospital of Oulu, Oulu, Finland.
authors.forename: Erika
authors.initials: E
authors.lastname: Jääskeläinen
authors.affiliation: Lapland Hospital District, Finland.
authors.forename: Eeva-Maija
authors.initials: EM
authors.lastname: Mylläri-Figuerola
authors.affiliation: National Institute of Health and Welfare, Helsinki, Finland.
authors.forename: Paula M
authors.initials: PM
authors.lastname: Salo
authors.affiliation: National Institute of Health and Welfare, Helsinki, Finland.|Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland.
authors.forename: Tiina
authors.initials: T
authors.lastname: Paunio
mesh_terms: D000368:Aged; D001110:Arctic Regions / Q000453:epidemiology; D001714:Bipolar Disorder / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D012307:Risk Factors; D012424:Rural Population; D012621:Seasons; D012720:Severity of Illness Index; D012890:Sleep
keywords: bipolar disorder; distress; endophenotype; high risk family; mood; seasonal variation