A study published in the journalNature Neurosciencesuggests that mammals born in a winter light cycle undergo alterations in their biological clocks that affect them during adult life. The finding of the influence of exposure to light during the first months of life couldexplain why the risk of depression, bipolar disorder, schizophrenia, and other mental illnesses is higher for people born in winter. ? The biological clock regulates mood in humans ?, explains Douglas MacMahon, a biologist at Vanderbilt University in Tennessee (USA). If there is a mechanism similar to that detected in mice for humans, “it could not only have an effect on a large number of behavioral disorders, but alsowould affect the personality“, adds the researcher.
In their experiments, McMahon and his colleagues grew two groups of mice for three weeks in summer light cycles (16 hours of light and 8 hours of darkness) and in winter cycles (8 hours of light and 16 hours of darkness. ). A third group grew up with 12 hours of light and 12 hours of darkness. By analyzing their brains, the scientists found that the activity of thekernel supraquiasmático(NSQ), where the “biological clock” is housed, varied according to exposure to light. Thus, those born in summer had a peak of activity in the neurons of this region at dawn, which continued for ten hours. In those born in winter, the peak of activity lasted until an hour after sunrise and could last 12 hours more (instead of 10) after the changes of season. According to McMahon, this means thatwinter-born mice exaggerated the response to the change of season, which bears an enormous resemblance to what happens in theemotional affective disordersuffered by some people at the beginning of winter.
