The Chemistry of Love

Sunday, February 7

With Valentines' Day around the corner, I thought it might be apropos to offer a run-down of the biochemical changes that occur when we're in love. Or, stated otherwise, what's the formula for Love Potion Number Nine?

First of all, let's not confuse love with fluid hydraulics. That's what Viagra's for, and it can help to overcome erectile dysfunction by promoting circulation, but it doesn't recreate the sublime feeling of infatuation. In fact, while erectile dysfunction drugs may help men have sex, they seem to do little or nothing when given to women in clinical trials.

This may have given rise to the saying, popular among sex researchers, that a woman's most important sex organ is . . . her brain.

Not to be confused with sexual arousal, the term "Limerance" refers to that state somewhere between agony and ecstasy where the heart goes pitter-patter for one's love object.

The brain neurotransmitter serotonin clearly has something to do with it. The ultimate serotonin-releasing drug is MDMA, better-known by its street-name Ecstasy. It produces feelings of rapturous love, and users report transcendent interpersonal encounters, or even getting stoned contemplating ordinary objects. Interestingly, it impedes sexual performance, so it's more about Platonic love. And users of lesser serotonin-releasing anti-depressants like Prozac (an SSRI or serotonin reuptake inhibitor) often report sexual dysfunction.

Then, of course, there are the sex hormones estrogen, progesterone, testosterone and DHEA. Higher levels of estrogen promote female sexual behaviors, while progesterone doesn't do much, and testosterone and DHEA promote libido in both men and women. In fact, low levels of DHEA in women are predictive of loss of libido. Testosterone unreliably promotes sex drive in women, suggesting true love is not about testosterone.

Phenylethylamine, or PEA, has been getting lots of press lately because it activates brain centers responsible for loving feelings. It has an amphetamine-like effect, and therefore has addiction potential. Chocolate has a high PEA content, hence the hypothesis that a Valentine's Day box of chocolate may be an aphrodisiac, or alternatively, a consolation prize for the real thing.

But scientists now report that PEA is broken down during the process of digestion and may be poorly absorbed. So the "buzz" people get from chocolate may be just from the good taste, the sugar, rich fat, and caffeine.

Pheromones may play a stealth role in attraction. These molecules are part of a primitive signaling system that involves the very ancient olfactory system that is a direct pipeline to the emotional center of the brain, the hypothalamus. Sometimes pheromones can be detected as attractive "funk", but often they are undetected and hit us "under the radar", subliminally influencing bonding behaviors.

Clearly endorphins, our body's own homemade opiates, are part of the "high" that's associated with love. Again, as with OTC pain meds and heroin, think strong addiction potential: Robert Palmer had it right in his memorable rock lyric "You know you're gonna have to face it, you're addicted to love." Then there's oxytocin, an interesting hormone that gets released when there's physical contact. A slow dance or a hug can bathe you in this affinity-reinforcing hormone that may be the key to pair-bonding in mammals. Touch deprivation takes a toll on health, because oxytocin triggers a profound relaxation response.

No discussion of the chemistry of love would be complete without mention of dopamine, the neurotransmitter responsible for motivation and reward. Hooked gamblers banging away at the slots in Vegas or Atlantic City are stoking brain levels of dopamine with every lever pull. Dopamine is also profoundly associated with risk-taking behavior like extreme sports--or illicit affairs.

So profound is the effect of dopamine on behavior that users of drugs that rev dopamine--commonly used for restless leg syndrome or Parkinson's Disease--sometimes depart from their staid ways and embark on serial affairs. Malpractice suits commonly award aggrieved plaintiffs big sums when marital breakups are triggered.

Bottom line, love is sublime, but akin to madness and intoxication. It's a force of nature to be reckoned with. Maybe we should just study the brain chemistry of Tiger Woods for an inside peak at the chemistry of love. And he just got out of rehab!