Love's first rush is a private madness between two people, all-consuming and, if mutually felt, endlessly wonderful.
Couples think about the other obsessively -- on a roller coaster of euphoria when together, longing when apart.
"It's temporary insanity," says Helen Fisher, an evolutionary anthropologist at Rutgers University.
Now, from her studies of the brains of lovers in the throes of the initial tumble, Fisher has developed a controversial theory. She and her collaborator, psychiatrist J. Anderson Thomson of the University of Virginia, believe that Prozac, Zoloft, Paxil and other antidepressants alter brain chemistry so as to blunt the intense cutting edge of new love.
Fisher and Thomson, who describe their theory in a chapter in the book, "Evolutionary Cognitive Neuroscience," aren't talking just about the notorious ability of the drugs to damp sexual desire and performance, although that, they believe, plays its part. They think the drugs also sap the craving for a mate -- perhaps even the brain's very ability to fall in love.
And that would be bad news, given the widespread use of antidepressants in this country -- about 10 percent of adult women and 4 percent of adult men take the drugs, according to a 2004 report by Centers for Disease Control and Prevention's National Center for Health Statistics.
Although they still lack solid evidence that more Americans are having trouble falling in love these days, the scientists do have animal and laboratory science along with some human studies to whet their research appetites.
For one thing, there's brain chemistry. The chemicals involved in the heart-pounding fall over the cliff into another's life, including dopamine, norepinephrine and serotonin, are the very chemicals altered by many anti-depressants.
Fisher cites animal studies showing, for example, that female prairie voles, naturally loyal to one mate, lose interest in him when dopamine is suppressed. The early human version of mate-pairing -- romantic love -- is also associated with increased activity in dopamine pathways. And SSRI antidepressants suppress that activity.
SSRIs also are known to curb obsessive thinking, the kind of focused state that is central to the first blush of romance.
For both these reasons, Fisher suggests that SSRIs could jeopardize intense romantic love.
There are few studies on the effects of antidepressants on aspects of love beyond libido and sexual performance. But in an intriguing experiment, one Canadian psychologist, Maryanne Fisher (no relation to Helen), reported evidence in a small 2004 study of what she termed "courtship blunting" in women taking antidepressants.
Asked to rate the attractiveness of men's faces, women taking the drugs rated the men more negatively and breezed through the pictures faster than women not on antidepressants.
There is also anecdotal evidence -- and although such stories may be anathema to hard science, they can provide the basis for research questions. Thomson collects them.
A 20-year-old man who had been on antidepressants from the ages of 15 to 18 was reluctant to take them again, despite feeling depressed. "No one told him about the sexual side effects. In retrospect, he realized he had the sexual side effects and that might have contributed to his not dating," Thomson says.
Any drug that has sexual side effects, Thomson says, could well blunt other chemicals the brain uses to intently focus on one person or to work up the obsession necessary to fall in love in the first place.
Then there was the 42-year-old single woman who had not been on a date in the eight years she had been taking an antidepressant. "She had not felt any desire (to date) for at least that period of time," he says.
Jerry Frankel, a urologist from Plano, Texas, who's been married for more than 40 years, was so conflicted about his experience on antidepressants he wrote to a national newspaper.
"My usual enthusiasm for life was replaced by blandness," he wrote. "My romantic feelings for my wife declined dramatically." He was willing to risk depression again in order to regain his zest for romantic depth.
Fisher and Thomson's theory is new enough that many therapists say they've never heard it discussed.
But Richard Tuch, psychoanalyst at the New Center for Psychoanalysis, says he has long been concerned, especially for adolescents, that if pharmaceuticals interfere with sexuality, they also might be interfering with a basic system that teens require to learn about the opposite sex. Still, he's cautious about sounding an alarm. "Antidepressants can save a person's life," he says.
Mental health experts like him already fear that, with recent publicity about suicidal risks in adolescents taking antidepressants, people whose lives could be improved or even saved with medications won't take them. Prescriptions for antidepressants for people 18 and younger fell by 20 percent since the Food and Drug Administration issued a warning in March 2004 that the drugs might increase the risk of suicide, according to research published in the Sept. 2, 2005, issue of Psychiatric News.
If people think the drugs will hamper their ability to find Mr. or Ms. Right, psychiatrists say, even more might avoid the potentially life-saving medications.
Fisher doesn't quarrel with the drugs' benefits for many with chronic, severe depression. But she worries about people who take the drugs to get through a break-up, a death or a job loss, then keep taking them.
"I'm concerned about well-adjusted men and women who go through a crisis and start taking antidepressants," she says. "They continue taking them, not realizing they may be suppressing these other systems."
Physicians, she says, aren't asking enough of the right questions when they ask their patients about side effects. Lack of awareness of a potentially troubling side effect -- becoming blase about romance -- is reminiscent of the years immediately after the first SSRI, Prozac, was approved in 1988.
At that time, reports were that only about 6 percent of patients suffered sexual side effects, but the low rate is now understood to have resulted because doctors failed to ask questions about sex and patients were reluctant to bring it up. A later analysis put that figure at about 30 percent, and a 2001 study at as high as 73 percent. It is one of the top reasons that people stop taking the drugs.
Doctors might be getting savvier about warning patients about the potential for sexual side effects. But most probably are not asking patients if they feel a blunted drive to search for love.
So far, there is no evidence that a dulling of romantic interest is a universal antidepressant side effect. And when it does appear in people who need the drugs to live and function, doses might be adjusted, or medications changed, Fisher says.
Some scientists dismiss Fisher and Thomson's theory. "Antidepressants tend to tone down the emotions. But they don't interfere with the ability to fall in love. No," says Otto Kernberg, director of the Personality Disorders Institute at the New York Presbyterian Hospital and author of six books on love.
But Tuch says the theory is challenging. "I think it's a call to the psychiatric community to study this. She's raised the question. Now it's our responsibility to look into it," he says.
Until more is known, Thomson has some suggestions for people on antidepressants.
"Regularly ask, 'Do I still need to be on them?' If you're having sexual side effects, ask if everything is being done to mitigate them, because those responses might also be linked to unconscious romantic desires.
"And ask yourself, 'How is this affecting my relationships?'.