Seventy-three percent of U.S. kids consume caffeine on any given day, according to a 2014 Pediatrics paper; a Yale study found that middle-schoolers who imbibe energy drinks are at a 66 percent higher risk for hyperactivity than their peers who abstain. Kids' caffeine usage is also linked to depression and substance abuse.
Adults suffer too. Caffeine withdrawal was added to the Diagnostic and Statistical Manual of Mental Disorders in 2013. "It's seen frequently, often alongside anxiety disorders," says David Salvage, a New York psychiatrist who specializes in addiction.
Even more alarming is the growing popularity of powdered pure caffeine, readily available in bulk on eBay. In 2014, the Food and Drug Administration, spurred by two lethal overdoses, warned that people should avoid the stuff, but an outright ban is unlikely.
One teaspoon of powdered pure caffeine is equivalent to roughly 25 cups of coffee.
One of the barriers to safe consumption is that regulation is all over the place, says Murray Carpenter, author of Caffeinated. "If you put 200 milligrams of caffeine powder into a 5-hour Energy Shot, it's regulated as a supplement," he says. But press it into a tablet, like NoDoz, and it's an over-the-counter medication. Blend it into six soft drinks and it's a food."
Even the military, which has long used caffeine-enriched foods to increase soldier alertness, is researching new methods for mental boosts, says Betty Davis, leader of the Performance Nutrition Team at the U.S. Army Natick Soldier Systems Center in Massachusetts. "We're looking to see if improving soldiers' gut health with dietary compounds is a good alternative," she says. Their findings could ultimately yield better, safer energy for the masses.