Love and Science: The Chemistry of Chemistry

Originally published in the Toronto Star on November 18, 2003.  In which we discover that ‘madly in love’ means something entirely different to a scientist

“I know I love her, Weebo. Every neuron in my limbic system is saturated with phenylethylamine.”
— Flubber, starring Robin Williams

A taut throat, pounding heart and shortness of breath might well describe symptoms of some terrible disease, and yet it’s remarkable how easily we can transpose them with the temperaments of love.  Are the lyrics of the lovesick — yellow stomach butterflies, deafening heartbeats, insomnia under a balcony — mere metaphors or empirical biology? Scientists have had a lot of success dissecting the love phenomenon. But far from contradicting the musings of Shakespeare in As You Like It (“Love is merely a madness; and, I tell you, deserves as well a dark house and a whip as madmen do”), research has only confirmed the spooky kinship of insanity, ailments and love.

Many of the same chemicals that govern romantic love are also factors in anxiety disorders and mental illness.  Helen Fisher, an anthropologist at Rutgers University in New Jersey, suggests the love phenomenon can be divided into three distinct phases: lust, infatuation and attachment — each governed by a different cocktail of chemicals.

And Albert Einstein said, “Gravitation can’t be held responsible for people falling in love.” But he didn’t say anything about dopamine, phenylethylamine or testosterone …

“And my heart went boom!”
— “When I Saw Her Standing There” by The Beatles

The first stage of love is lust — raw sex drive — and according to Fisher, it evolved in order to “initiate the mating process with any appropriate partner.”

Lust is dominated by the hormone testosterone. Although both men and women produce it, a woman’s testosterone level tends to hover at about 10 per cent of a man’s. This accounts for the indiscriminate courtship behaviour often observed in males, such as yelling, “Hey baby,” from a moving car.

Too much testosterone in men may lead to some of the behaviours we associate with the stormy lovers of literature and history — Lord Byron, Don Juan, Heathcliff, Deuce Bigalow.  High testosterone levels have also been associated with aggressive behaviour in prisoners and with violent tendencies in sex offenders.

One is very crazy when one is in love.”
— Sigmund Freud

The second stage of love — infatuation — is the great human obsession.

Bewitched lovers sigh of thudding heartbeats, loss of appetite, sweaty palms and arrested breathing. Romantic rhetoric or fact of physiology?

You guessed it.

The body’s sympathetic nervous system is responsible for providing quick energy during emergencies.

That means it is programmed to release special chemicals when faced with an urgent, “nerve-wracking” stimulus — which could be anything from a sabre-toothed tiger to an attractive woman.


Norepinephrine (similar to adrenaline) is released from nerve endings acting on the heart, blood vessels and lungs. The U.S. Surgeon General notes that this produces instant surges in blood pressure and heart rate.


Essentially, the chemical’s release renders one ready for action.


But if the sympathetic nervous system malfunctions, the results can be devastating.


Irregular levels of norepinephrine have been associated with anxiety disorders — including panic attacks, phobias, obsessive compulsive disorder and post-traumatic stress syndrome.


According to Health Canada, 12 per cent of Canadians are victims, as well as Michael Jackson, Laurence Olivier, Charles Darwin, and the poets W.B. Yeats, Robert Burns and Tennyson.


Hug me till you drug me, honey …”
— Brave New World by Aldous Huxley

Phenylethylamine (PEA), is sometimes called “the love drug.”


It’s found in chocolate and strawberries as well as in the body. When one is “in love,” PEA floods the brain, triggering the release of dopamine and creating a “high” — a sense of confidence, boundless energy and intense joy.


Although the PEA/dopamine “highs” are not as fleeting as those engendered by drugs such as speed and cocaine (chemical cousins of PEA and dopamine), they are still relatively short-lived.


And when the “thrill is gone” — or the PEA — many couples part ways.


Fisher has christened this, “the four-year itch.” She estimates that love-induced dopamine and PEA levels tend to drop off after the first 18 months to four years of a relationship — a finding eerily congruent with the Canadian divorce rate, which peaks after four years of marriage.


Might as well face it, you’re addicted to love …”
— “Addicted to Love” by Robert Palmer


Dopamine functions in the limbic system — the brain’s “pleasure centre” — but it has a darker side, playing a major role in drug and alcohol addiction, according to the University at Buffalo’s Addiction Research Unit. It has been suggested that “commitment phobics” who repeatedly hop from one short, intense affair to the next are literally “addicted to love” — to the titillation of the infatuation high.


Just how addictive is pleasure? In the 1950s, James Olds wired up rats so that they could use a lever in their cages to self-stimulate their brains’ limbic systems.


The results were astonishing: The rats became so addicted to the sensation (pressing the lever as many as 5,000 times in a single hour) that they no longer cared about eating — eventually starving themselves to death in a pleasure supernova.


Grow old along with me! The best is yet to be, the last of life, for which the first was made.”
— Robert Browning

When the high of infatuation melts away, that doesn’t mean the romance has to end.


Science shows that passion can blossom into a sense of great attachment. Attachment is the final stage of the love saga and evolved, says Fisher, “so that mated pairs would be more committed to jointly raising offspring.”


The feeling is mediated by the chemical serotonin, which leaves one feeling calm and serene. Like all of the chemicals of love, too much or too little can wreak havoc on the brain. Irregular levels of serotonin have been associated with depression, bipolar disorder and manic-depression.


Another factor in attachment is the “cuddle chemical” oxytocin, which, according to Paul Zak of Claremont University, has little effect on new partners but deepens the tenderness between familiar ones. The release of oxytocin can be prompted by gentle skin-to-skin touch (including massage) and may be released by men or women during sexual intercourse.


Oxytocin also plays a definitive role in the fanatical monogamy of prairie voles, which mate literally for life (if one partner dies, in 80 per cent of cases the survivor will remain celibate until death).


You don’t bring me flowers any more …”
— Neil Diamond and Barbra Streisand



Unfortunately, not all relationships make it to the attachment stage. About 3 per cent of mammals instinctively mate with one partner for life — but humans are not one of them. So it is no surprise that 17 per cent of married Canadians have been cuckolded by their spouses, according to a 2001 Ipsos-Reid poll.


Much of what we know about monogamy is based on studies of the prairie vole, conducted by Thomas Insel and Larry Young at Emory University in Atlanta. The vole is a rodent that in captivity will spend up to 50 per cent of its time huddled with its mate. After mating for the first time, the male becomes indifferent or hostile towards other voles, preferring to hide out with his mate, cuddling or copulating (sometimes as often as 50 times in 48 hours).


The dependence of the male vole’s behaviour on vasopressin (VAP), a chemical released during copulation, is staggering. When VAP is suppressed, the voles abandon their love nest and quickly begin sniffing around for new partners.


Could a “fidelity drug” for compulsive cheaters be in our future? Scientists are divided over the relevance of these studies to humans.


Insel and Young observe that VAP is released during human sexual intercourse, but Claire McLoughlin of the Royal Society of Chemistry in England notes that the chemical’s capacity to “dry out” the faithless may be too literal to be of much use. Artificial intake of VAP, she says, results only in a “decreased production of urine.”


Which means science hasn’t quite figured out an antidote for love. It appears we’ll all have to let nature take her mysterious chemical course.



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