Mouse model reveals a cause of ADHD - Rockefeller University Although its typically considered an adolescent curse, ADHD actually affects about five percent of adults as well. New research in a mouse model of attention deficit/hyperactivity disorder suggests that the root of the psychiatric disorder might be the over-activity of a protein that regulates dopaminergic pathways. The work suggests a path toward new treatments for symptoms including inattentiveness, over-activity and impulsivity. The cause of ADHD is unknown, but there is increasing evidence that dopamine, a neurotransmitter involved in the brains reward-motivation system, is involved. Scientists have found that the level of dopamine, and the D2 receptor it binds to, are involved in the progression of ADHD, as well as four connected regions in the frontal region of the brain, two of which are directly linked to reward and motivation.