Proponents of drug therapy claim that symptoms of ADD are caused by neurological dysfunctions within the brain and point to studies done with PET scans confirming that there is a definite difference in brain functions between groups of individuals diagnosed with Attention Deficit Disorder, and those without it. According to their theory, specific chemicals called neurotransmitters may be lacking in individuals with ADD, and where subsequent to taking medication, brain activity appeared to be much more like that of the normal group... Full Text