Rainy weather is often associated with bleak moods, but new research has found that rain and other environmental factors, like temperature and pollution, may not play a significant role in determining mood. Instead, sunlight appears to be the key to good mental health. The study, published in the Journal of Affective Disorders, looked at data from 16,452 university students living at a northern latitude and receiving counseling. The students answered the Outcome Questionnaire 45.2, a test that measures markers of psychological distress, including symptoms of depression and anxiety, feelings of loneliness and conflict, and difficulties in social roles. Researchers compared the students’ answers to weather and pollution data from the place and time they completed their questionnaire. This data included wind chill, wind speed, rainfall, solar irradiance, temperature, and pollution level. They found that:

• Seasonal sunlight time was associated with the degree of psychological distress: reports of psychological distress were increased during periods of decreased hours of sunlight.
• Other aspects of weather, like rainfall and temperature, were not associated with higher psychological distress.
• Initially, pollution appeared to be associated with higher psychological distress; however, when sunlight time was taken into account, this relationship was no longer evident.

The researchers hope that this discovery may help guide treatments for people susceptible to psychological and emotional distress. Future research may help us to understand how much sunlight we need to support mental health and whether people living in places with less seasonal variation in sunlight hours are still affected by periods of relatively low sunlight time. These findings may also encourage more research into the usefulness of light therapy.
Source: Journal of Affective Disorders