Adderall 20 mg is a commonly prescribed dose of a central nervous system (CNS) stimulant that contains a combination of amphetamine and dextroamphetamine. It is used in the treatment of Attention Deficit Hyperactivity Disorder (ADHD) and, in some cases, narcolepsy. This medication helps increase attention and decrease impulsiveness and hyperactivity in individuals with ADHD by affecting certain chemicals in the brain.