Only licensed medical professionals can diagnosis ADHD. A comprehensive diagnosis includes a clinical evaluation, medical exam and standardized tests. (See ADHD Diagnosis.) However, the most important factor to any ADHD diagnosis rests in the Diagnostic Statistical Manual of Mental Disorder’s symptoms' checklists. Suspected patients who have six out of nine symptoms over a period of six months under one or both of the categories of hyperactive/impulsive and/or inattentive will earn the diagnosis.