Currently, the most promising research about the causes of attention deficit disorders is being done in the area of neurochemistry. It is thought that individuals with ADD do not release enough of the chemicals needed to send information from the brain stem to other parts of the brain (Goldstein & Goldstein, 1990). Deficits in attention occur when the central nervous system is unable to produce enough of a family of neurotransmitters called the catecholamines. Most important to the attentional system are, norepineephrine and dopamine. These neurotransmitters are thought to affect a wide variety of behaviors, including the regulation of attention, inhibition, and motor responses (Lownthal 198). .
Heredity is thought to be the most common cause of ADD. The problem tends to run in families and to be associated with other problems of impulse control. When family histories of patients with ADD are taken, a common finding is that other close family members also have symptoms of attentional problems. Cumulatively, studies demonstrate a genetic predisposition for attention deficit disorders (Lowenthal 207).
The finding that the incidence of ADD in adopted children is higher than for biological children supports the genetic theory of ADD. The speculation is that the biological parents of the adopted children probably had attention deficit disorders. Twin studies also support the genetic theory of ADD. Researchers at the University of Minnesota conducted a large-scale longitudinal study of twins who were reared apart. The study found that even when identical twins were reared apart, they had similar characteristics in terms of hyperactivity and inattention (Lowenthal 207). Researchers concluded that genetics or heredity plays a significant role in the characteristics of hyperactivity and inattention.
Students with AD/HD differ significantly from their peers in their ability to concentrate and control impulses.
