Canadian winters are known to be long, dark and sometimes agonizing for fair weather enthusiasts. But has winter been wrongfully charged as a cause for low moods and discontent?
New findings from Dr. Ian Colman, Canada Research Chair in Mental Health Epidemiology and associate professor at the Faculty of Medicine’s School of Epidemiology and Public Health, now challenge the idea that people are more depressed during winter.
He and his colleague, Dr. Simon Øverland from the Norwegian Institute of Public Health, led a systematic review of the literature on seasonality and symptoms and found no general population shift toward lower mood at any regular intervals throughout the year.
“As mental health researchers, we are often asked by journalists whether winter blues and ‘Blue Monday’—the alleged ‘most depressing day of the year’—are real,” said Dr. Colman. “And we have always been skeptical about whether or not there’s evidence to support these popular claims. So, we decided to do a systematic review of all the studies on this topic by looking at depression in the general population and whether it varies by season.”
For this study, a team involving researchers from the United Kingdom, Norway and Canada worked together to review over 2,000 possibly relevant papers, choosing 41 to include in this evaluation, which was published online in Epidemiology and Psychiatric Sciences on April 22, 2019.
“There are a lot of different ways to measure depression. Some studies use clinical diagnoses, while others use a variety of questionnaires,” explained Dr. Colman, describing the lack of consistency in this research area. “There are also a lot of variations in the way researchers categorize seasons—how many seasons are there, and which months are considered part of winter, all vary between studies.”
For this reason, one of the crucial steps for the team was to come up with a set search strategy, as a systematic literature review looks at everything that’s been published on a topic. This task was led by uOttawa librarian Lindsey Sikora, who helped complete an exhaustive search so as to ensure that nothing was missed.
“For our review, the team excluded studies that explicitly mentioned seasonal patterns in questionnaires so as to avoid confirmation and memory biases by the participants,” said Dr. Colman. “Instead, we narrowed our focus to studies that had no specific intent of measuring seasonality in relation to mood and depression, but happened to assess depression among survey respondents at different times of the year, and subsequently analyzed the data for any distinguishable relationship between season and mood.”
Among the 41 studies included in this review, only 13 suggested more depression in winter, while the remaining 28 suggested no seasonal pattern or seasonality outside of winter, or had inconclusive results.
“For us, this means that either increased prevalence of depression exists on such a small scale that it’s hard to observe, or people cope very well and have management strategies—such as exercise and social interactions— that minimize its effects entirely,” concluded Dr. Colman.
