Ever noticed that all your friends turn a year older at the same time? There's a good reason for that: science confirms more women are getting pregnant during the Christmas period.
According to a report by Indiana University (IU) and the Instituto Gulbenkian de Ciência in Portugal, baby births spike in September, with scientists citing the festive period 9 months prior as the cause.
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"The rise of the web and social media provides the unprecendented power to analyse changes in people's collective mood and behaviour on a massive scale," says co-leader of the study, Luis M. Rocha from IU.
"This study is the first 'planetary-level' look at human reproduction as it relates to people's moods and interest in sex online."
The conclusion? Interest in sex surged during cultural or religious celebrations. This was in line with birth rates 9 months later around the month of September.
This is the biggest study of its kind to date. Because the report includes nations from both the Northern and Southern Hemispheres, researchers were able to dismiss the idea that seasonal change brought about higher libido.
"We didn't see a reversal in birth rate or online interest in sex trends between the Northern and Southern hemispheres - and it didn't seem to matter how far people lived from the equator," says Rocha.
"Rather, the study found culture - measured through online mood - to be the primary driver behind cyclical sexual and reproductive behaviour in human populations.
"We observe that Christmas and Eid-Al-Fitr are characterised by distinct collective moods that correlate with increased fertility. Perhaps people feel a greater motivation to grow their families during holidays when the emphasis is on love and gift-giving to children. The Christmas season is also associated with stories about the baby Jesus and holy family, which may put people in a loving, happy, 'family mood.'"
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