Attention-deficit hyperactivity disorder (ADHD/ADD) is a neurobehavioral disorder of childhood onset characterized by severe, developmentally inappropriate motor hyperactivity, inattention, and impulsiveness that result in impairment in more than one setting. Attention-Deficit Hyperactivity disorder (ADHD), or hyperkinetic disorder (HKD), is a diverse neurodevelopmental condition characterised by symptoms of inattention, hyperactivity and impulsivity, and can have a significant impact on affected individuals' There are two key medical classification systems used to define ADHD: The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders - 5th Edition (DSM-5TM) medical classification system which defines ADHD as "a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or development" The International Classification of Diseases 11th Revision (ICD-11), which defines ADHD as "a persistent pattern of inattention and/or hyperactivity-impulsivity that has a direct negative impact on academic, occupational or social functioning".