Crazy in Love ... or Just Plain Crazy?

When Beyonce told the world she was “Crazy in Love,” she might not have been exaggerating.

Love, the saying goes, can make you do crazy things — one only need look at Britney Spears (search), Angelina Jolie and Jennifer Lopez for examples A, B and C.

But experts say there are scientific reasons why people tattoo their lovers' names on their bodies, "run away" together, shack up and even marry too soon.

"Love is a drug, it behaves like a drug, it involves the same basic chemicals that drug abuse involves," said anthropologist Helen Fisher (search), author of "Why We Love: The Nature and Chemistry of Romantic Love." (search) "You'll walk out of college, give up your job, move to a different country. You'll will walk down the aisle with somebody you don’t know," she told FOXNews.com.

Fisher, who has done extensive research on the physiology of love, said passion triggers the same areas in the brain that are involved in substance abuse and other addictive behaviors.

"You have intensely elevated energy — you can walk or talk all night long — elations, mood swings, obsessive thinking about the person. You go through inappropriate behaviors to win the person. You have increased tolerance for the person — you want more and more. Everything else takes a back seat," she said.

Hence the devastation some people feel when love ends.

"If the person walks out on you, you have real withdrawal — suicide, lethargy, like a crash. You get over it, and eight months later you can relapse — hearing a song the two of you had together. And the obsessive thinking comes back."

Perhaps one the most common "crazy" things couples do when they're in love is get married after a short courtship.

Among celebrities, Spears famously tied the knot with childhood friend Jason Alexander "just for the hell of it" last January, and had the marriage annulled 55 hours later. Less than a year later, she did it again, jumping into matrimony with dancer and father-of-two Kevin Federline.

J-Lo married dancer Cris Judd seemingly out of nowhere not long after breaking up with boyfriend P. Diddy — and we all know how that story ended. Her latest groom, Latin crooner Marc Anthony (search), popped up only months after her split from Ben Affleck.

And A-listers certainly aren't the only ones who do this.

Ted Huston, Ph.D., professor of human ecology and psychology at the University of Texas, spent 15 years studying the relationship between the length of time a couple dated and marital success — and found that the closer a courtship is to average length (two years, four months), the more successful the union.

"The bottom line is it depends on why you’ve fallen in love so quickly. If indeed it’s based on an idealized image not adequately based on experience, then it’s a problem," he said. "Most of the people who fall in love and marry quickly are plunging into a not-well-grounded relationship."

However, everybody knows a couple married 50 years who knew they were "the one" for each other and high-tailed it to the altar.

"There are people others grasp almost immediately as wonderful in relationships –- not so much as their soul mates, but people who make good soul mates," Huston said.

But beelining it down the aisle is not the only crazy thing people do for love. Some seem to believe that a romance is not official until it is tattooed in permanent ink.

Johnny Depp (search) famously tattooed “Winona Forever” on his right arm, in honor of Winona Ryder, only to change it to “Wino Forever” after they broke up. Pamela Anderson honored then-husband Tommy Lee with a “Tommy” tattoo, eventually changing it to “Mommy.” And Angelina Jolie had “Billy Bob” tattooed on her arm in large black letters when she was married to Billy Bob Thornton, which she now either covers up or has had removed.

More recently, supermodel Kate Moss is said to have tattooed in a heart the initial of British rocker Pete Doherty, and he hers. And "Arrested Development" starlet Portia de Rossi has reportedly been having treatments to laser off an "F.G." tattoo — ex-girlfriend Francesca Gregorini's initials — from her ring finger, now that she's dating Ellen DeGeneres.

Bonnie Jacobson, a psychologist who specializes in sexuality, says getting a tattoo of your lover's name is like trying to defy the laws of nature.

"Some of us really crave getting high and we wish this high would be forever. The tattoo is almost saying to the gods of the world — 'I will stay in the level of intensity.' But you can't."

Celebrities in particular have the misfortune of inscribing their love in something even more permanent than ink: celluloid.

Angelina and Billy Bob made out passionately in public and wore vials of each other's blood, and paparazzi gleefully snapped up the damage. Ben Affleck demonstrated his love for J-Lo by literally kissing her behind in one of her videos, seemingly without a thought that the romance would end only months later.

And now they're forced to see these tapes, over and over again.

Should they have known better? Not necessarily. Fisher said when you're in the first months of ecstasy, you never think such images will come back to haunt you.

"When you feel madly in love, you honestly think it will last forever," she said.

But despite what the greeting cards say, passionate love doesn't even come close to surviving eternity. Fisher said the only really good study on the subject so far indicates it has a shelf life of 12-18 months — if there are no barriers to the relationship.

"If you're attending college on the other side of America, if one person is married to somebody else or if one person travels constantly, it can last a lot longer," she said.

While some people will stay together after the initial, frenzied period ends, many won't — and those who do probably won't be wearing vials of blood or making love on the subway.

"I don't think people married 25 years will say they spend all day writing their partner's name in their notebook," Fisher said.

But what about love at first sight? Fisher believes it exists, but said she herself would wait until the romantic phase is over before proclaiming it to the world.

"If you get a tattoo and the person dumps you in a year and half, you'll want to cut your own arm off," she said.