The report at the link below says popular energy drinks are a rising public health problem.
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.
The report explains what could happen to some people. Blood pressure goes up, heart rate goes up and then they'll start to feel the effects. Heart racing, heart skipping, panic-attack symptoms and irregular heart symptoms and worse.
Energy drinks also contain other substances that are "completely unregulated" and can add to the stimulant nature of the drink.