Researchers suggest that seasonal variations in depressive symptoms are much more common in women than men.
Researchers at the University of Glasgow in the United Kingdom have found that women are much more likely than men to experience seasonal variations in depressive symptoms, with these symptoms peaking during the winter months.
Study co-author Daniel Smith, of the Institute of Health and Wellbeing at Glasgow, and team have recently reported their results in the Journal of Affective Disorders.
Seasonal affective disorder (SAD) is a form of depression that comes and goes with the seasons. It is estimated that SAD affects approximately 5 percent of people in the United States in any given year.
Symptoms of SAD include feelings of depression, worthlessness, low energy, fatigue, and lack of interest in usually enjoyable activities, or anhedonia. SAD most often begins in the fall, with symptoms usually subsiding by the summer months.
Previous research has suggested that women are much more likely to be affected by SAD than men.
In order to find out more about how SAD varies by sex, Smith and his team conducted a cross-sectional analysis of more than 150,000 adults who were part of UK Biobank, which is health database of half a million people in the U.K.
A 'sex-specific biological mechanism'?
The researchers looked at the depressive symptoms of participants during each season, as well as symptoms of low mood, anhedonia, tiredness, and tenseness.
The team also looked at the link between symptoms of depression, the length of days, and the average outdoor temperatures.
The analysis revealed that women experienced seasonal variations in symptoms of depression, as well as symptoms of tiredness and anhedonia, but these seasonal variations were not found in men.
Symptoms of depression, tiredness, and anhedonia in women were strongest in the winter months, the team reports.
These findings persisted after accounting for social and lifestyle factors, including smoking, alcohol consumption, and exercise.
Additionally, the researchers found that longer days were associated with a reduction in low mood and anhedonia among women, but they were also linked to an increase in tiredness.
However, the team notes that "associations with day length were not independent of the average outdoor temperature preceding assessment."
According to Smith, their study provides further evidence that women may be more prone to seasonal variations in depression than men.
"We don't yet fully understand why this should be the case, but it was interesting that the changes were independent of social and lifestyle factors, perhaps suggesting a sex-specific biological mechanism."
"Clearly," explains Smith, "this is a complex but important area which requires further study." He goes on to say, "Clinicians should be aware of these population-level sex differences in seasonal mood variation, to aid the recognition and treatment of depressive symptoms across the calendar year."
The researchers note some limitations to their study. They point out, for example, that they were only able to evaluate a subset of depressive symptoms, and symptoms were self-reported.