Ritalin is the prescription brand name of the drug methylphenidate, a stimulant of the central nervous system (the brain and spinal cord). Its effects lie somewhere between those of caffeine and those of amphetamine drugs: Ritalin improves concentration, decreases appetite, produces an elevated mood, and can interfere with sleep.

In the mid-1950s Ritalin was first sold as a mood enhancer and was described as having less abuse potential than amphetamine. However, within a few years medical journals published a number of dramatic reports of its abuse and toxicity. Like the amphetamines and other stimulant drugs, methylphenidate is a controlled substance. This means that, although it has medical uses, Ritalin also has substantial abuse potential.

The main medical use of Ritalin is in the treatment of attention deficit/hyperactivity disorder (ADHD). A child may be diagnosed with ADHD if he or she is extremely active and/or has...