The science of energy drinks is still unsettled, especially for short-term effects. While a huge dose of caffeine may merely cause a serious case of the jitters, the long-term effects are far more problematic.
Energy drinks contain large amounts of caffeine. In small doses, caffeine serves as a stimulant. However, an excessive amount of caffeine can cause sleeplessness, nervousness and anxiety. More serious symptoms such as vomiting and high blood pressure can arise for some people. In fact, energy drinks have been connected to the deaths of at least thirteen people, though it is important to note that there has not been a clear causal relationship in those cases. The makers of energy drinks are not required to disclose the caffeine content of their products, but it is undoubtedly very high. Even those companies recommend drinking no more than two of their drinks per day, and probably not back-to-back.