Sex for spite, revenge, power and love - and everything else in-between!

Researchers in the United States have uncovered 237 reasons why people have sex.

The new research by scientists at the University of Texas in Austin is one of the most comprehensive studies on why people have sex.

The study has revealed hundreds of varied and complex motivations for getting sexually involved which range from the spiritual to the spiteful and just about everything else in between.

Some said they had sex to feel powerful, others to debase themselves, some wanted to impress their friends, others to harm their enemies.

The Texas psychologists David Buss and Cindy Meston identified four major factors and 13 sub-factors for why people have sex from a range which included the mundane, "I was bored," the spiritual, "I wanted to feel closer to God," the altruistic, "I wanted the person to feel good about himself/herself," to the manipulative, "I wanted to get a promotion."

They say the four major factors for having sex are:-

• Physical.... such as reducing stress, to feel pleasure, improve or expand experiences and the physical desirability of their partner.

• Goal-based.... including utilitarian or practical considerations such as "I wanted to have a baby," "I wanted to be popular," or "I wanted to give someone a sexually transmitted disease."

• Emotional.... such as love, commitment and expression -- "I wanted to say 'thank you."

• Insecurity.... including self-esteem, a feeling of duty or pressure or to guard a partner from straying.

The researchers say why people have sex is extremely important, but rarely studied and many scientists assume the answer is obvious, but people have different reasons for having sex, some of which are rather complex.

The study, published in the August issue of Archives of Sexual Behavior.