The seasons are decisive in many respects: for animals, they are crucial in terms of reproduction and hibernation, for example; for humans, it also affects our mood, hormones, immune system, neurotransmitters … Now, a recent study carried out by researchers at the University of Liège (Belgium) suggests that the seasons influence our intellectual capacity, making it more vulnerable or more consistent at certain times of the year and that it does not affect us all equally.
According to Gilles Vandewalle, co-author of the study, people with seasonal affective disorder or have depression for a few months, are even more vulnerable to the effects that seasonal changes have on our brain.
For their experiment, the researchers analyzed 14 men and 14 women, averaging 21 years of age, at different times of the year between May 2010 and October 2011. Participants spent 4.5 days in labs where they were not aware of external changes, neither daylight nor the weather. They had no access to the outside world. They then used brain scans while the participants tested their abilities to pay attention and recall information in the short term.
The results revealed that the participants’ attention skills were much better around the summer solstice – especially in June – and worsened around the winter solstice, specifically in December. Regarding short-term memory, it was better in the fall and worse in the spring.
Although experts do not know how the seasons affect the brain but “they are the most likely responsible,” according to Vandewalle. Changes in humidity, temperature, length of day, and social interaction between people could be involved as well.
The study has been published in the journal Proceedings of the National Academy of Sciences (PNAS).
