Ritalin (methylphenidate) is a central nervous system stimulant. It affects chemicals in the brain and nerves that contribute to hyperactivity and impulse control. It produces such effects as increasing or maintaining alertness, combating fatigue, and improving attention.‌ Meta-analyses and systematic reviews of magnetic resonance imaging studies suggest that long-term treatment with ADHD stimulants (specifically, amphetamine and methylphenidate) decreases abnormalities in brain structure and function found in people with ADHD.