A new government study is calling popular energy drinks "a rising public health problem" that is sending more and more people to the emergency rooms.
The study, from a survey of U.S. hospitals by the Substance Abuse and Mental Health Services Administration, said that the number of emergency-room visits linked to energy drinks had doubled in four years - from 10,000 in 2007 to 20,000 in 2011.
And of those 20,000 ER visits in 2011, 42 percent had mixed the energy drink with another stimulant such as Adderal or Ritalin or with alcohol. Fifty-eight percent had consumed just the drink.
Dr. Allen Taylor, chief of the cardiology division at Georgetown University Hospital, explained what could happen to some people when they consume an energy drink.
"Blood pressure goes up. Heart rate goes up and then they'll start to feel the effects," Taylor said. "Heart racing, heart skipping, panic-attack symptoms. Irregular heart symptoms and worse."
Taylor said that energy drinks also contained other substances that are "completely unregulated" and can add to the stimulant nature of the drink.
The American Beverage Association, the industry trade association, told ABC News today that the drinks were safe and denounced the hospital study, saying the limited information makes it "impossible to understand the actual role - if any - of energy drinks in these hospital visits."
The group also pointed out that "mainstream energy drinks contain about half the caffeine of a similar size cup of coffeehouse coffee."
The Food and Drug Administration is looking at this new study.
"We will examine this information to determine whether it can be used to assess whether energy-drink products can be legitimately linked to the types of adverse events reported in the … data," an FDA spokesman said.