Why babies born in summer have sunnier dispositions

London: The season in which a baby is born can have a dramatic effect on their biological clocks function, according to a new study.

The study conducted on mice might explain why people born in winter months have a higher risk of a number of neurological disorders including seasonal affective disorder (winter depression), bipolar depression and schizophrenia.

"Our biological clocks measure the day length and change our behaviour according to the seasons. We were curious to see if light signals could shape the development of the biological clock," said Vanderbilt University Professor of Biological Sciences Douglas McMahon.

The team found slowing of the gene clocks in winter-born mice compared to those born on a summer light cycle. They also discovered that the biological clocks and behaviour of summer-born mice remain stable and aligned with the time of dusk while that of the winter-born mice varied widely when they were placed in a summer light cycle.

"The mice raised in the winter cycle show an exaggerated response to a change in season that is strikingly similar to that of human patients suffering from seasonal affective disorder," McMahon commented.

The new study raises the possibility that seasonal variations in the day/night cycle may affect personalities in humans.

"It`s important to emphasize that, even though this sounds a bit like astrology, it is not: it`s seasonal biology!" McMahon added.

The study was published online on December 5 by the journal Nature Neuroscience.