The drug methylphenidate is marketed as the brand Ritalin and used to treat children and adults with ADHD. As of 2011, according to the U.S. Centers for Disease Control and Prevention, 11 percent of Americans aged 4-17 were diagnosed with ADHD. The high number of people diagnosed with ADHD means that there is a vast amount of prescription drugs to treat this condition in medicine cabinets across the US. Ultimately, some of these drugs get diverted into the hands of non-prescribed users, such as college students who believe they may be able to improve their studying and performance on exams by taking these drugs.
The use of cognition-enhancing drugs by healthy individuals in the absence of a medical indication spans numerous controversial issues, including the ethics and fairness of their use, concerns over adverse effects, and the diversion of prescription drugs for nonmedical uses, among others. Nonetheless, the international sales of cognition-enhancing supplements exceeded US$1 billion in 2015 when global demand for these compounds grew.