ADHD medications such as Ritalin are stimulants. They work be either increasing the release of dopamine or blocking the reuptake of dopamine. In either case the net result is increased stimulation. In fMRI scans, patients with ADHD show hypoactivity in their frontal cortex. After receiving medication, patients show increased activation and reduced symptoms of ADHD. If a single medication does not prove effective others can be substituted. With all the psychopharmacological drugs made for use with ADHD, they have an effectiveness of reducing symptoms in 85-90% of all people (Rowland, 168). People who do not benefit from such treatments are usually people who suffer adverse side effects in which the harm outweighs any benefits.
Those affected are usually boys, causes of ADHD are not really known but it may be due to any number of reasons including but not limited to: lower than average cortex size, hypoactivation of the frontal cortex, genes, exposure to teratogens, and a dopamine deficiency. Symptoms include inattention, hyperactivity, and impulsivity. ADHD is categorized into three subtypes: mostly inattentive, mostly hyperactive-impulsive, and combined; with most patients falling into the latter category.