Coconut Grove resident Dr. Elizabeth Leight has four kids, including two teenage girls ages 14 and 15 years old. Naturally, their calendars are packed with schoolwork, sports and social engagements. So when it comes time to booking an appointment at the orthodontist or an enrichment class after school, she insists that they phone up and schedule these things themselves.

“I know I’ll be the one driving them there,” Leight says. “But this empowers them. They gain control over their own time.”

They also become desensitized to the harsh winds of competitive materialism plaguing so many of South Florida’s teens, according to new science. Researchers have long known a few things about young adults and money, mostly that each generation cares more about cash than the one before, and as a result, is more miserable. But now they’ve found surprising results proving teens who feel in control of their schedules — with not too little or too much free time — think less about caustic shopping and feel better about themselves.

Perhaps Leight — who says she could probably to afford spend on designer items but doesn’t find her kids particularly interested — knows this time affluence is a perception, not a reality. That’s why having power over their own schedules — in addition to a few other tricks for time management — can improve their views of the day and instantly boost well being.

“As parents we have to allow our children to make their own decisions about how they spend their time,” says James Roberts, professor of marketing at Baylor University in Waco, Texas. “Most kids have either no free time or too much — and those are the two worst groups to be in.”

That’s because over-scheduled kids are quick to buy clothes, sunglasses and other status items as a coping strategy to reduce stress, Roberts says. Those with too much time in their hands become captivated by marketing ploys on television and by merchandise in malls. What he found after surveying 1,300 9th- and 10th-grade students is that teens who perceive their schedules to be manageable, lined with many fulfilling activities but also the downtime required for creativity to blossom, were the least materialistic and more likely to forge fulfilling friendships.

“When we base our happiness on money and compete with others for possessions, our well being is diminished,” Roberts says. “What really makes humans happy is how we feel about ourselves and the quality of the relationships we have.”

Problem is, Roberts can’t say how many free hours or minutes a kid needs because the sweet spot doesn’t depend on conventional time measurements but rather on the teen’s own perception of them. Two kids can respond quite differently to the exact same schedule.

If eliminating extracurricular activities for your stressed out teen is not an option — as is sometimes the case for, say, working parents — there are ways to change her perception of the program she’s following, says Dr. Ingrid Vasiliu-Feltes, assistant professor of psychiatry and behavioral sciences at the University of Miami Miller School of Medicine. People respond positively to a choice they make themselves, she says. So after explaining to your teens you can’t pick them up until 7 p.m., provide a list of classes available during that time and let them select how they spend their time. If the schedule is still packed with a dreaded activity, link it to a positive one. For example, you can tell a baseball-enthusiast that he can have his piano lesson before or after practice — his choice. Same goes for other non-negotiable engagements, such as dentist appointments.