Winter birth may alter biological clock
Being born in winter could make your long-term biological clock tick slower, according to a new study on mice. The findings could explain why people born in winter are at higher risk of mental health disorders, such as bipolar, depression, schizophrenia and seasonal affective disorder.
Researchers raised mice from birth in either 'summer' light cycles, with 16 hours of light each day, or 'winter' light cycles, with only eight hours of light each day. After being weaned for three weeks the mice were shuffled into different light cycles. Finally all mice were put in a continuously dark environment to remove any influence from light on their biological clock.
Those reared in summer behaved the same in both winter and summer cycles, becoming active at 'dusk' for 10 hours and then resting for 14 hours. However, when mice reared in winter were put into a summer cycle they stayed active for an extra hour and a half above normal.
The exaggerated response to the change in season is similar to that of patients suffering from seasonal affective disorder.
To explore the effect further, the researchers used GM mice engineered so that their biological clock neurons glowed green when active. The behaviour of the mice was found to match the activity of these neurons. Neuron activity in the winter-born mice peaked earlier and lasted longer than in the summer-born mice.
More research is needed to see just how quickly after the birth the biological clock is set and whether the affects are permanent.
Read more about depressive disorders here.