It is not a myth. During winter, states of depression and melancholy are more frequent, and in the Nordic countries, with long winters of almost total darkness, the suicide rate is higher than in other parts of the planet. A scientific study published in the journal Nature has shown that mice exposed to lesser and more irregular amounts of light suffer from depression and experience learning disabilities .
The scientists, from Rider and Johns Hopkins Universities, divided the mice into two groups, the first subjected to a normal cycle of 12 hours of light and 12 hours of darkness, and the second with an abnormal cycle consisting of 3.5 hours of light and 3.5 hours of darkness. As an indicator of depressive disorder, the researchers compared the corticosterone levels of both groups, and found that mice subjected to an irregular cycle had higher concentrations of the same. This hormone is secreted in response to moments of anxiety, which indicates a greater tendency to suffer from depressive processes.
On the other hand, the lack of light also caused learning difficulties. Using a test in which the animals had to locate a hidden platform, the scientists observed that mice exposed to abnormal cycles needed more attempts to complete the search successfully . “These results indicate a learning deficit in the brain region of the hippocampus,” they state in their study.
In addition, the authors studied the effect of treatment with the antidepressant fluoxetine or Prozac in mice with light deficiencies, verifying that it reduced their depressive behavior.
