Have you ever had sex to feel closer to God?
How about to change the topic of conversation? Or because you wanted to get rid of a headache or break up a rival's relationship?
Perhaps you just wanted to debase yourself.
A new study, published today in the journal Archives of Sexual Behavior, suggests that the reasons we have sex may be much more varied than previously thought.
"In the scientific literature, they've really only been talking about the most obvious reasons why people have sex -- because they're in love, because it feels good and because they want to have a baby," says study author Cindy Meston, associate professor of psychology at the University of Texas at Austin.
"But after 17 years of doing research into women's sexuality, it was apparent to me that people are having sex for all sorts of reasons that weren't being discussed in the literature," she said.
The researchers first sampled 203 men and 241 women, ranging in age from 17 to 52. They asked them to list all the reasons why they ever had sex.
Some of what they found surprised the researchers.
They received answers from "The person smelled nice" to "I wanted to burn calories" to "I wanted to get out of doing something."
"Some of the negative motivators -- the ones that had to do with revenge, or manipulation, or competition -- really surprised us," says Meston. "One of the darkest answers was 'to give someone else an STD,' and that really surprised us."
Some of the other answers they found had nothing to do with pleasure, emotional attachment or procreation -- what many would consider the usual reasons for sex.
"There were lots of things about enhancing psychological or physical well-being, like getting rid of a headache, cramps or stress," says Meston.
The researchers then took their compiled list -- 237 motivations for making love in all -- and gave it to undergraduate students at the University of Texas. The students indicated on a questionnaire how frequently each of the reasons led them to have sex in the past.
Answers for men and women differed somewhat, but the top reason for sex -- "I was attracted to the person" -- was the same for men and women.
"There is a sense of men just wanting to have sex more for physical reasons and women for emotional reasons, but that's just not as great as people thought," says Meston.
"Men kind of get a bad rap in the media about this -- that they're just hormone machines. The fact that those gender differences were not substantial during college, when the hormones are pumping, is interesting."
And women, who are traditionally viewed as the gender more likely to use sex to gain status or resources, were not alone in their endeavors.
"We found that men have sex to gain status too," Meston says. "What they get may be different, but there's no difference in using sex to get ahead."
Meston acknowledges that their study only asked college students to rate their reasons for sex, and that there may be cultural factors at play, but she is planning more research. She says that the study could help people figure out better ways to get the safe-sex message out.
Other sex experts agree that the study's findings are useful.
"We don't often study the phenomenological aspects of sex," says Evelyn Resh, the director of sexual health services at Canyon Ranch in Lenox, Mass.