There’s a common belief that the weather affects our mood, that we tend to become more depressed in the winter and that summer brings an emotional lift. This has been researched before in small studies that have found inconsistent results but a new study published in Psychiatry Research tested the idea on almost 14,500 people and found no link to weather, while the seasonal effects did not follow the common belief: depression was more common in summer and autumn.
The researchers, led by Dutch psychologist Marcus Huibers, tested both the effect of daily changes in weather and the influence of the season. They sent out thousands of invitations to to people in Holland to complete a standard depression diagnosis questionnaire on the internet, in waves of a few thousand every week, over 18 months.
This allowed the researchers to check the exact day’s weather against people’s mood states.
Neither that day’s temperature, the amount of sunshine or rainfall had any immediate effect on mood, and the seasonal changes were not what you’d expect from ‘common knowledge': men had seasonal peaks of major depression and sad mood in the summer, while women had seasonal peaks in the autumn.
Although there are some people who do seem to have depression triggered when winter arrives (a condition diagnosed as ‘seasonal affective disorder’ or SAD) this link doesn’t seem to exist in the public as a whole.
I currently live in Medell√≠n, a city without seasons, to the point where it is nicknamed as ‘the city of eternal spring’. The locals says it used to be possible to tell the difference between the rainy seasons and dry seasons but over the last few years it’s simply been impossible to make any distinctions.
Interestingly, this has an effect on how we assess people for dementia. One of the ‘orientation’ questions for the widely used ‘Mini-mental state examination’ or MMSE evaluation is ‘what season is it?’.
As no-one knows what season it is, the assessment has to be scored out of 29 rather than 30, or it has to be replaced with something ad-hoc like ‘what part of the day is it?’.
However, it would be also interesting to find out whether depression varies here by time of year to understand whether this effect is really to do with season, or perhaps to do with the significance of the date.
For example, self-harm and suicide has been found to vary more by significant public holidays than by time of year.
Link to PubMed entry for depression, weather and season study.