In a bid to break the world record for the most people to simultaneously renew their wedding vows, 629 couples gathered at the Carnegie Music Hall in Pittsburgh on Feb. 10, 2008. (Andrew Rush, AP)

In his theory of relativity, Albert Einstein said a lot of things about gravity and the attraction between independent bodies. But when it came to explaining relationships he was quick to absolve the force, pointing out it isn't responsible for people falling in love.

And he was right. When it comes to human relationships it's biochemistry, not physics, that takes at least some of the credit — or blame — for the amorous phenomenon.

Cuddle Party workshops, the brainchild of two relationship coaches in New York, are meant to help people rediscover non-sexual touch and affection. (JamesBeeler/BlackStarImages 2006)

In the past few decades, scientists have linked neurotransmitters and hormones in the human body to everything from the "butterflies" of new love, to an individual's desire to stray or stay devoted for life.

This research has prompted clinical approaches to "lovesickness." Scientists have dabbled with boosting feelings of trust and generosity through intranasal doses of hormones, and one company has promoted the acquisition of "love chemicals," such as oxytocin, from a room full of strangers.

But do complex emotions such as infatuation, passion and devotion really boil down to a series of chemical reactions? And even if they do, is our science savvy enough to explain why fools fall in love?

Taking the red pill

Research indicates that falling head over heels for someone affects the same chemicals in your limbic system — the part of the brain associated with survival behaviours, memory and emotion — as some illicit drugs. Specifically, two neurotransmitters — dopamine and serotonin — are key players in the game of love, says Dr. Jose Lanca, a professor at the University of Toronto who specializes in the pharmacology of drug addiction.

"Feelings toward people, as well as mood disorders, are events that are based on these chemicals … and the very same principles are targeted by drugs of addiction," Lanca said.

For example, phenylethylamine (PEA), a substance that occurs naturally in the body, is thought to play a role in romantic excitement. The amphetamine-like chemical has been shown to increase the effect of dopamine, dubbed the brain's "pleasure chemical."

Dopamine's activity — which is also upped by drugs such as caffeine, cocaine and crystal methamphetamine, a highly addictive drug — can induce dilated pupils, increased heart rate and energy, and restlessness. These are all symptoms also associated with the "butterflies" of attraction.

Lovesickness

But what causes the depression, anxiety, and preoccupation commonly referred to as "lovesickness"?

It turns out people struck too hard by cupid's arrow have levels of serotonin — the neurotransmitter associated with mood — that are similar to those of patients diagnosed with obsessive compulsive disorder (OCD).

In the late 90s, a psychiatrist at the University of Pisa, Donatella Marazziti, looked at individuals who had been "lovestruck" for less than six months, and found a reduced concentration of serotonin in the blood. This may explain why early-stage romance can turn into obsession, or lead to behaviours such as constantly checking your phone, e-mail or Facebook to see if your new partner has made contact.

In a separate study, the researcher also discovered that concentrations of hormones such as cortisol, follicle-stimulating hormone and testosterone change in the presence of romantic love. They return to normal levels after 12 to 24 months, even for couples that don't break up.

Other research has suggested that the brain becomes less sensitive to amphetamine-like PEA, or that levels of PEA begin to drop, after the initial infatuation.

If we do, in fact, "fall out" of these chemical stimulations as time goes on, how do some relationships last a lifetime?

Making the high last

When infatuation fades, researchers believe oxytocin, or "the hormone of love," is the fuel that keeps the red fires burning in long-term relationships.

"There's convincing evidence that oxytocin is involved in mediating stability, pair bonding, and monogamy; the enduring parts of love," said Dr. Hans Zingg, a professor at McGill University who specializes in the hormone's receptor system.

In the bloodstream, the chemical functions as a hormone that induces lactation and labour in women. But during intimacy and orgasm, oxytocin is also released by both sexes. It acts on the brain as a neurotransmitter to make relationships last … at least for prairie voles.

Cuddle Party co-founder Reid Mihalko estimates anywhere from 7,000 to 10,000 people, mostly singles, have attended cuddle parties — which are mediated by a trained "cuddle lifeguard" — since the inaugural get-together in early 2004. He says snuggling with strangers may seem weird or uncomfortable to some, but it's actually a natural physical need that many of us gravitate toward as children and then repress as adults. (JamesBeeler/BlackStarImages 2005)

The rodents are serially monogamous, setting them apart from other vole species and the vast majority of other mammals. Zingg explained that research has shown that the prairie vole's fidelity seems to hinge on oxytocin.

"If you inject an antagonist [during mating] so that oxytocin is not active anymore, prairie voles don't stay together; you don't have this partnership bonding," he said.

"On the other hand, if you take a prairie vole that isn't having sex and inject oxytocin, you can induce partnership bonding that usually only occurs after mating."

Although humans get a similar surge of oxytocin during sex, and there is evidence the hormone increases a person's feelings of trust and generosity when taken through the nose, we're a far cry from the prairie vole degree of faithfulness. Three in 10 Canadians say they've been cheated on by a current or past partner, according to an Ipsos Reid poll.

The difference may lie in the way our oxytocin receptors are laid out, Zingg said. Studies comparing the prairie vole to its promiscuous cousin, the montane vole, found this distribution — not the amount of oxytocin — accounted for the opposing behaviours.

"In humans, [the receptors] might be distributed in such a way that oxytocin is not acting as efficiently as it is in the prairie vole; or in some individuals it might, and in others not so," Zingg said.

"Now you have a good excuse if you are not faithful to your partner: Say 'well, my oxytocin receptor is in the wrong place; what can I do?'" he joked.

In search of the big 'O'

But what if you could experience the chemistry of love without baggage or explanations?

Apparently you can get an oxytocin fix, no strings attached, from a room full of strangers. All it takes is $30 and the will to get close. Cuddle Party workshops, the brainchild of two relationship coaches in New York, are meant to help people rediscover non-sexual touch and affection.

But when up to 30 strangers converge in a room, change into pyjamas, and get their cuddle on for hours at a time, chemical release is "kind of like the whip cream on the banana split," according to co-founder Reid Mihalko.

"Studies have shown that sustained touch — for more than 20-second bursts — begins to activate the body's machinery to release oxytocin and some other hormones," he said.

"When you can create feelings of safety and find people to play with responsibly, the body does all these wonderful things and there's all this sensation and fun."

Reid estimates anywhere from 7,000 to 10,000 people, mostly singles, have attended cuddle parties — which are mediated by a trained "cuddle lifeguard" — since the inaugural get-together in early 2004.

Reid says snuggling strangers may seem weird or uncomfortable to some, but it's actually a natural physical need that many of us gravitate toward as children but repress as adults.

"When you look at a bunch of kids, they're just kind of laying all over each other like little monkeys," he said.

"That need for touch is so important to our development as children, and it doesn't go away; it's important to our psychological well-being as adults as well."

Complicated chemistry

Even if love turns out to be nothing more than a series of chemical reactions, Lanca says one thing it will never be is simple.

"Not a single neurotransmitter can be represented as people falling in love; it's all too complex," the University of Toronto's Lanca said.

"We know a lot of the pieces of the puzzle, but we can't single out a single one. If we could, we would have the cure — and there ain't no cure for love."

The author is a Toronto-based freelance writer.