"Uppers" is a term used to refer to drugs containing amphetamines, methylphenidates and other derivatives. These drugs are psychostimulants that increase the speed at which chemical messages are sent to the brain. All forms of amphetamines are addictive.
As a result, uppers tend to increase energy, concentration and even self-confidence. Legal amphetamines—such as brand-name drugs Ritalin, Concerta and Vyvanse—are usually prescribed to treat a variety of conditions including attention-deficit/hyperactivity disorder (ADHD), excessive daytime sleepiness resulting from narcolepsy, Parkinson's disease and, occasionally, depression.
Street versions of these drugs include speed as well as the strongest and most dangerous of them all: crystal methamphetamine, or in common parlance, crystal meth. Methamphetamine is a more potent stimulant than amphetamine, its parent drug, because much greater amounts of the drug get into the brain.