Boys — but not girls — who consume caffeine see an increase in their blood pressure, according to a new study exploring caffeine's effects on teens.

"Adolescents are among the fastest-growing consumers of caffeine, and yet very few empirical studies have focused on this population," study researcher Jennifer Temple of the University at Buffalo, said in a statement. "It is imperative that we understand the impact of caffeine use on adolescents."

Researchers asked 26 boys and 26 girls ages 12 to 17 to drink Sprite soda which had been allowed to go flat. The drink contains no caffeine, but the researchers added 50 milligrams of caffeine, 100 milligrams of caffeine or 200 milligrams of caffeine to some of the kids' sodas. They then tested the kids for changes in their blood pressure and heart rate every 10 minutes for one hour, according to the study.

At the end of the hour, the researchers gave the kids a questionnaire and an opportunity to eat all they wanted of Skittles and Smarties candies (which have high sugar levels and low fat levels), potato chips and Doritos chips (which have low sugar levels and high fat levels) and M&Ms and Twix candies (which have high sugar levels and high fat levels).

The boys who drank the highest amounts of caffeine had the greatest increases in blood pressure compared with boys who ingested less or no caffeine, the study found. There was no relationship found between blood pressure and caffeine consumption in girls.

In addition, the participants who ingested the most caffeine ate more high-sugar snack foods in the laboratory than the low-caffeine consumers.

In their answers to the questionnaire, boys and girls gave different reasons for consuming caffeine, the researchers found. Boys were more likely than girls to say they consumed caffeine "to get energy," "to get a rush" and for "athletic performance."

Boys and girls were nearly equally as likely to report consuming caffeine because their friends were consuming or because they wanted help concentrating.

Previous studies have shown that teen girls consume energy drinks less frequently than boys. The University of Buffalo researchers wrote that girls could be drinking less because they do not experience the positive effects of caffeine as boys do. But it could also be that girls are not experiencing the positive effects of caffeine because they consume the drinks less frequently.

The study was published in the December issue of the journal Experimental and Clinical Psychopharmacology.

Pass it on: Caffeine can have different physiological effects on boys and girls.