Pon Farr

The Pon farr is a neuro-physiological condition in Vulcans from the Star Trek continumn. Every seven years, adult Vulcans experience an overwhelming and irresistable urge to take a mate - failure to do so could result in death. It is considered an intensely private condition that they rarely speak of with anyone outside of Vulcan society.

More about the Pon farr at Memory-Alpha.