Have yourself a horny little Christmas

South Africans are among the best in the world when it comes to having themselves a horny little Christmas.

Internet searches including "sex" and "porn" are nearly four times higher than normal at Christmas in a country where 80% of people describe themselves as Christians.

And the birth rate in September - nine months after the festive season - is 10% higher than normal, the biggest variation in the world.

Researchers who uncovered the data found a similar pattern pointing to more interest in sex in Muslim countries in the weeks of Eid-ul-Fitr and Eid-ul-Adha, as well as a steep decrease during Ramadan.

And they said their findings put paid to theories that pregnancy spikes were related to biology, temperature, libido, daylight or the December solstice. In fact, they relate to holidays.

"Our results provide evidence that the sexual and reproductive behaviour of human populations is mostly driven by culture and that this interest in sex is associated with specific emotions, characteristic of major cultural and religious celebrations," the US and Portuguese team wrote in Scientific Reports this week.

South Africans' Google searches related to sex - the top five search terms they used were "porn sex", "porn", "free sex", "sex videos" and "sex pics" - increased by a factor of 3.815 in Christmas week over 10 years.

Only six countries among the 129 in the survey had a higher number, with Nigeria (4.65) topping the league, followed by Luxembourg, Kenya, Switzerland, the UK and Ghana.

In an attempt to understand higher interest in sex during the holidays, the researchers conducted a "sentiment analysis" of Twitter posts and found that people appear to feel happier, safer and calmer during the holidays.

"Christmas and Eid-ul-Fitr are characterised by distinctive collective moods that correlate with increased fertility," said Luis Rocha of Indiana University, who led the study.

"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."

Rocha said the findings could help to pinpoint the best dates to launch public awareness campaigns encouraging safe sex in developing countries.

"The strong correlation between birth rates and the holidays in countries where birth-rate data is available - regardless of hemisphere or the dominant religion - suggests these trends are also likely to hold true in developing nations," he said.

"These types of analyses represent a powerful new data source for social science and public-policy researchers."

The findings had other implications: "Hospitals should be prepared for an increase in STD testing and possibly even abortions in the weeks following holidays and when the corresponding collective mood is observed at other times of the year."