Seasonal variation in specific depressive symptoms: A population based study

Abstract

IntroductionDepression varies with season in Canadian youth. However, the symptom profile of seasonal depression may differ from that of non-seasonal depression. Here we evaluate which specific symptoms vary by season. MethodsUsing data from the 2015/2016 Canadian Community Health Survey, cross-sectional analysis was conducted. The Patient Health Questionnaire-9 (PHQ-9) was administered to respondents in 8 provinces/territories (n ≈ 53,000), with interviews conducted throughout the year. Seasonal effects were assessed using quadratic terms in a logistic regression model. Guided by previous literature and analysis, analyses were stratified by age into youth (age 12–24) and adult (age 25+) groups. ResultsIn the youth, 8 items of the PHQ-9 exhibited a significant season variation: lack of interest/pleasure, feeling depressed/down, hypersomnia/insomnia, lacking energy, poor appetite/overeating, feeling bad about yourself/ like a failure, being slow/fidgety, and trouble concentrating. In the adult group, only sleep and poor appetite/overeating exhibited a seasonal effect. Notably, symptoms of self-harm/suicide did not demonstrate seasonality in either group. LimitationsDue to use of cross-sectional data and a brief symptom rating scale, conventional criteria for Seasonal Affective Disorder or Major Depressive Disorder with seasonal variation could not be applied. Also, treatment status of respondents was not assessed in the survey, therefore possible confounding by this variable could not be assessed. ConclusionsA seasonal pattern was observed in most symptoms of depression in Canadian youth, whereas in adults, only symptoms related to sleep and appetite disturbance displayed seasonal variation.