Focus.impulsv.hyper. Adhd: symptoms including attention deficit (inability to maintain focus), impulsivity, and/or hyperactivity. Symptoms are typical and normal for 4 year olds, but start affecting all aspects of life (academic, social, family, athletic) when they persist beyond. Vanderbilt forms help objectively. Behavior modification, school involvement, and mainly stimulant medication are used as treatment.
Focusing problem. Functional MRI studies can define the brain regions involved in adhd. A simple model for adhd focusing problems is the old cathode ray tv screens with focus controls; if it is out of clear focus, then the images are quite difficult -frustrating- to distinguish. Thus, those with adhd have to struggle to pay attention, and are often distracted and can be irritable.
Changes in brain . structure & chemistry found in persons with adhd validate the diagnosis of ADHD as a neurodevelopmental disorder with significant symptoms of Inattention &/or Hyperactivity/Impulsivity that impact learning, peer interaction &/or behavior, often over a person's lifespan. CHADD.org is a good resource to learn about ADHD diagnosis, treatment and legal rights of people with ADHD at all ages.