Energy drinks can be dangerous for teenagers, according to a new report published in a pediatrics journal.

The drinks are particularly dangerous when they are combined with alcohol, CBS News reports. The drinks can cause rapid heartbeat, insomnia, high blood pressure, anxiety and obesity, researchers write in Pediatrics in Review.

"They contain too much caffeine and other additives that we don't know enough about. Healthy eating, exercise and adequate sleep are better ways to get energy," said lead author Dr. Kwabena Blankson, a U.S. Air Force major and an adolescent medicine specialist at the Naval Medical Center in Portsmouth, Virginia.

Many teens are not aware that mixing alcohol and energy drinks can make them feel less drunk than they actually are, the researchers noted. They wrote that drinking just one caffeinated beverage mixed with alcohol can be equivalent to drinking a bottle of wine and several cups of coffee. A 16-ounce energy drink has about 160 milligrams of caffeine, compared with 100 milligrams for an average cup of coffee.

Dr. Blankson said teens should not have more than 100 milligrams of caffeine daily. He added that other additives found in energy drinks, such as sugar, ginseng and guarana, increase caffeine's effects in energy drinks.

A government report released last month found the number of emergency room visits involving energy drinks doubled from 2007 to 2011, reaching more than 20,000. The report, from the Substance Abuse and Mental Health Services Administration (SAMHSA), found most cases involved teens or young adults. SAMHSA calls consumption of energy drinks a "rising public health problem." About 42 percent of emergency room cases in 2011 involved energy drinks combined with alcohol or drugs such as Adderall or Ritalin.

Drinking alcohol and energy drinks together has become trendy, but it can also be risky. Marketed to kids, often through "new media" marketing campaigns and "grassroots" strategies using youth-oriented imagery and slogans, the new alcohol energy drinks have high alcohol content, sometimes as high as 12% as compared with 5% for a typical can of beer. Click here to learn more.