"The caffeine content of energy drinks varies over a 10-fold range, with some containing the equivalent of 14 cans of Coca-Cola, yet the caffeine amounts are often unlabeled and few include warnings about the potential health risks of caffeine intoxication," says Dr. Roland Griffiths, one of the authors of the article that appears in the journal Drug and Alcohol Dependence this month.
The scientists highlight the fact that the market for such drinks is growing at a fast pace, and their advertisements mainly focus on their performance-enhancing and stimulant effects.
They believe that appropriate warning labels are necessary to help consumers realise whether they are getting a little or a lot of caffeine.
"It's like drinking a serving of an alcoholic beverage and not knowing if its beer or scotch," says Griffiths.
The researchers says that most of the drinks advertise their products as performance enhancers and stimulants, something that may put young people at risk for abusing even stronger stimulants, including some prescription drugs.
Caffeine intoxication, a recognized clinical syndrome included in the Diagnostic and Statistical Manual of Mental Disorders and the World Health Organization's International Classification of Diseases, is marked by nervousness, anxiety, restlessness, insomnia, gastrointestinal upset, tremors, rapid heartbeats (tachycardia), psychomotor agitation (restlessness and pacing) and in rare cases, death.