Winter-born babies’ personalities appear to have a higher risk of mental disorders like schizophrenia or bipolar depression, compared to those born during the summer season. A recent study showed that winter births have a tendency to affect the biological clock of the baby and this can happen later on in their lives. This study was conducted on mice and the story had been published in a journal last week.

Biological clocks are regulators of human moods; it is in an individual’s behavior that brings about how he reacts towards events. There is a possibility that babies weaned during winter would differ in behavior than those who were weaned in summer as having experimented on a group of mice.

The mice were grouped into three divisions: some were weaned in summer (light schedule), with 16 hours of light with eight hrs of dark, winter (cycle), with eight hours cycle of light and 16 hours of dark, with the third group weaned, experiencing 12 hours light and 12 hours of darkness in a day. All of them were put on a three-week period of observation.

Right after weaning time, the mice were reshuffled to fit into different light cycles. Half of the members of the group stayed behind their previous grouping while some were made to go with the others to experience new members’ presence. Twenty eight days have passed and all of them were made to go into continuous darkness environment, trying to eliminate light cues which influences biological clock. This can help the researchers determine the fundamental biological cycle of every mouse within the experiment zone.

The purpose is looking into the possibility that light cues might be instruments in shaping the mice’s biological clock; and it turned out to be positive. Summer mice’s usual behavior stayed the same, summer or winter season switching did not matter. Winter-born mice reacted otherwise as they kept the ten hrs on and fourteen hours off scheduling. However, those who transferred to summer mode stayed active 1.5 hours more.

In conducting this research, the mice were hereditarily engineered so that their bio clock neurons will glow in green once active. The glow can help them monitor the suprachiasmatic nucleus or SCN, an area in the middle brain that houses the biological clock. The behavior of the mice matched the activity in their suprachiasmatic nucleus. Those that are summer-born have their peak of activity an hour just after the end of the day and went onwards ten hours after. This represented normal behavior.

The winter-born have their peak activity a couple of hours before sunset and stayed on for 12 more hours. The other group, composed of the equal light subjects had varied reactions that were considered extremes, regardless of the season they have experienced after weaning time.

It is not known yet if humans will have the same responses to this early life exposure of light, but the closest that they can arrive at is that winter-born mice overstated reactions has a striking similarity to humans’ seasonal mental disorders.

Winter births raises risk for particular mental disorders and there are several factors that could be attributed to these risks; and these are the things that the researchers would like to find out next.