CHICAGO (CBS) — More and more these days, you see teenagers hanging out at your neighborhood coffee shop, craving a caffeine kick.

But what will it do for their health? CBS 2′s Mary Kay Kleist reports.

“It’s kind of like a coffee date,” Caroline Rubach, 15, said. “We just go out and drink coffee and talk.”

Amanie Aiyash is also 15. She’s having a caramel frappuccino with extra caramel. Rubach is having a pumpkin spice latte.

What they’re drinking is a lot of caffeine. The caramel frappuccino has 100 milligrams of caffeine in 16 ounces. Both the pumpkin spice latte and a cappuccino contain espresso. Each carry 150 milligrams of caffeine.

So more young teens are drinking coffee drinks these days, but what’s the harm?

Some health experts say that too much caffeine can ruin a good night’s sleep.

Mary Mullen is a pediatric dietitian at Rush University Medical Center.

“It could affect not only how much sleep they get at night, but it could be more of an interrupted type sleep,” Mullen said.

“It’s really annoying because you always are tossing and turning,” said teenager Chris Karkazis. “And you feel like you can’t sleep because you’re not in the right position, really it’s just the caffeine.”

Too much caffeine can lead to heartburn, intestinal upsets like constipation and diarrhea, heart palpitations, and short-term increases in blood pressure.

“It can cause them to get nervous and anxious,” Mullen said.

And that makes it hard to focus.

“If they’re a little more wired, I’m not sure the focus will be there for homework,” said Sherry Kenny, who is Chris Karkazis’ mother.

Her son drinks coffee out socially with friends, but not always at home. And, when he does, she notices a difference in his personality.

Kenny said, “It’s um, crabbier somehow.”

Experts told us teens should have no more than 100 milligrams per day, which is about one eight-ounce cup of regular coffee. But remember caffeine is also in chocolate, sodas and energy drinks.

Many of the kids we talked with say they like caffeine to jump-start the day.

If your teen is going to drink coffee, experts say don’t let them have it after 3 p.m. because it takes six to seven hours for the effects of caffeine to wear off.

It’s not known whether drinking coffee has any beneficial effects on teenagers because those studies haven’t been done.

But studies show adult coffee drinkers were less likely to have type 2 diabetes, Parkinson’s disease and fewer cases of certain cancers.