Troy Dayton pops a little white pill every morning. He's one of the 10 million Americans taking a daily antidepressant. But in his case, he says he was never depressed in the first place.

This 29-year-old political lobbyist is one of the happiest people you'll ever meet. He's constantly smiling, and says he wakes up belly-laughing two or three times a week. Dayton says he's an optimist by nature, and that his daily dose of Wellbutrin makes him feel even better.

"Wellbutrin makes me feel great," Dayton stated. "Wellbutrin made me feel clear-headed, much more able to focus. I don't think it means that I don't ever experience any sadness, but I think it makes me experience sadness in a very healthy way."

Dayton says a doctor first prescribed Wellbutrin for him 2 1/2 years ago, as an aid to quit smoking. Buproprion, the active drug in the antidepressant, helps smokers quit because it partially blocks the brain chemicals which keep them hooked. A recent study by UCLA researchers found that the drug may help break addiction to methamphetamine, too. Buproprion also increases the brain level of dopamine, a chemical linked to excitement, new experience and pleasure.

Psychiatrists stated that Dayton's use of Wellbutrin as a lifestyle drug is potentially dangerous, although little is known about the long-term effects.

"These medicines are not harmless," said Dr. Peter Kramer, author of "Listening to Prozac." Kramer said some doctors think that if you stay on antidepressants long enough, you'll come to rely on them. Other doctors believe they might trigger manic-depressive illness in susceptible people, he said.

Most antidepressants -- though not Wellbutrin -- are in a group of drugs known as selective serotonin reuptake inhibitors, or SSRIs. They prevent the body from re-absorbing the naturally occurring chemical serotonin, thus increasing serotonin levels in the brain. It's like plugging up a drain to keep running water in the sink.

Serotonin, like dopamine, is linked to good feeling. Those chemicals and others are released during any pleasurable experience, like a kiss, or eating a bar of chocolate. The release of endorphins, another chemical, is linked to the "runner's high" experienced by some endurance athletes.

Chemically, there's little difference between good feelings induced by medication and those occurring naturally. But the use of antidepressants by those who don't need them raises, for many, not just medical concerns but ethical flags as well. The concerns grow larger when the subject turns to illegal drugs. Millions of Americans take them, but few are willing to admit it. Once again, Troy Dayton is a rare exception. He said he takes Ecstasy, also known as MDMA, about once a year.

He likens the feeling it gives him to falling in love. "In certain moments, it's just this feeling of intensity. If your heart could jump out of your body and into the other person's, it would."

Dr. Julie Holland, a psychiatrist at New York University, says MDMA holds promise as an aid to psychotherapy for some patients, if taken under the guidance of a trained therapist under tightly controlled conditions. The federal government has approved early human trials

"Our understanding of the brain is still in its infancy," says Holland. "The SSRIs that I like to prescribe take really about two or three weeks before people start to feel them. The full effects won't kick in until about four to six weeks, or six to eight weeks."

By contrast, illicit drugs kick in almost immediately. Dr. Nora Volkow, director of the National Institute on Drug Abuse, says they produce pleasure - and often lead to addiction - using the same neural pathways that light up when people have sex or enjoy a good meal. She says these pathways also guide primal emotions like the satisfaction a mother gets from nurturing her infant.

"It's not that drugs create a new landscape in our brains," Volkow said. "Drugs hijack those landscapes that are there [already], that are extraordinarily important to motivate our behaviors."

Volkow says Ecstasy users are risking serious physical harm, including damaged neurons and deep depression. Government statistics show Ecstasy is linked to about 8,000 emergency room visits every year, mostly for overheating and dehydration.

Dayton is unrepentant about his drug use. "If we have the ability to have something better, then why not?" he asks. "However someone can sustain a certain level of happiness without hurting someone else, should be celebrated and not questioned."

Where antidepressants are concerned, Holland agrees. "I think it's sort of this puritanical mind set. You're supposed to sort of go it alone, and you don't need crutches unless your leg is broken," she said.

"[But] short of doing very advanced PET scans, where you're looking at receptors and neurotransmitters and things like this, it's hard to say who really deserves to take antidepressants and for whom it's a luxury. Having a private practice in New York City, I have a lot of luxury-minded patients who just know if they take something they'll feel a little bit better. And I'm okay with that."