New York, Jun 15 (IANS): If you are an early riser, you are significantly less likely to develop depression, according to researchers.

"Being an early type seems to be beneficial, and you can influence how early you are," said lead author Celine Vetter, Director at the University of Colorado-Boulder.

Conversely, people who are up till late at night are twice as likely to suffer from depression, studies have shown.

It is because the late chronotypes -- or night owls -- are less likely to be married, more likely to live alone and be smokers, and more likely to have erratic sleep patterns, the researchers explained.

Lack of sleep, exercise, less time spent outdoors, bright lights at night, and low exposure to daylight all can contribute to depression.

For the study, published in the Journal of Psychiatric Research, the team analysed more than 32,000 female nurses to explore the link between chronotype -- the propensity for the individual to sleep at a particular time during a 24-hour period, or sleep-wake preference, and mood disorders.

The results showed that even after accounting for environmental factors like light exposure and work schedules, chronotype -- which is in part determined by genetics -- appears to mildly influence depression risk.

"Our results show a modest link between chronotype and depression risk. This could be related to the overlap in genetic pathways associated with chronotype and mood," Vetter said.

However, early risers still had a 12-27 per cent lower risk of being depressed than intermediate types, while late types had 6 per cent higher risk than intermediate types (this modest increase was not statistically significant).

"This tells us that there might be an effect of chronotype on depression risk that is not driven by environmental and lifestyle factors," Vetter noted.

Vetter stressed that while the study does suggest that chronotype is an independent risk factor for depression, it does not mean night owls are doomed to be depressed.