Attention deficit-hyperactivity disorder is one of Attention deficit-hyperactivity disorder is one of the most common neurobehavioral disorders the most common neurobehavioral disorders that affects 3-7 percent of all American that affects 3-7 percent of all American children. It is characterized by inattention, children. It is characterized by inattention, hyperactivity, and impulsivity. According to hyperactivity, and impulsivity. According to the DSM-IV, symptoms must be present for at the DSM-IV, symptoms must be present for at least 6 monthsleast 6 months

• Are easily distracted, miss details, forget things, and Are easily distracted, miss details, forget things, and frequently switch from one activity to anotherfrequently switch from one activity to another

• Have difficulty focusing on one thingHave difficulty focusing on one thing

• Become bored with a task after only a few minutes, Become bored with a task after only a few minutes, unless they are doing something they think is fununless they are doing something they think is fun

• Have difficulty focusing attention on organizing and Have difficulty focusing attention on organizing and completing a task or learning something newcompleting a task or learning something new

• Have trouble completing or turning in homework Have trouble completing or turning in homework assignmentsassignments

• Don’t pay attentionDon’t pay attention

• Daydream, and become easily confusedDaydream, and become easily confused

• Have difficulty processing info as fast and Have difficulty processing info as fast and accurately as othersaccurately as others

• Struggle to follow instructions.Struggle to follow instructions.

• Fidget and squirm in their seatsFidget and squirm in their seats

• Talk nonstopTalk nonstop

• Jump around, touch / play with whatever they Jump around, touch / play with whatever they seesee

• Have trouble sitting still in places like school Have trouble sitting still in places like school and need to be constantly in motionand need to be constantly in motion

• Have a difficult time doing activities quietly.Have a difficult time doing activities quietly.

o Very impatientVery impatient

o Blurt out random things, show their emotions Blurt out random things, show their emotions without restraint, and act without regard for without restraint, and act without regard for consequencesconsequences

o Have difficulty waiting for their turnHave difficulty waiting for their turn

o Often interrupt conversations or others Often interrupt conversations or others activities.activities.

According to Dr. Russell A. Barkley, a Research According to Dr. Russell A. Barkley, a Research Professor in the Department of Psychiatry at Professor in the Department of Psychiatry at the State University of New York Upstate the State University of New York Upstate Medical University, and one of the leading Medical University, and one of the leading experts in ADHD, biological factors are a experts in ADHD, biological factors are a strong contributor to its occurrence.strong contributor to its occurrence.

In fact, he says that heredity/genetics makes the In fact, he says that heredity/genetics makes the largest contribution to the expression of the largest contribution to the expression of the disorder in the population.disorder in the population.

o The heritability of ADHD averages The heritability of ADHD averages approximately 80 percent meaning that genetic approximately 80 percent meaning that genetic factors account for 80 percent of the factors account for 80 percent of the differences among individuals in this set of differences among individuals in this set of behavioral traits.behavioral traits.

o If a parent has ADHD, the child has a 42-If a parent has ADHD, the child has a 42-57% chance of also having it.57% chance of also having it.

Barkley looked into several twin studies in Barkley looked into several twin studies in regards to ADHD regards to ADHD

o He found that the probability of both He found that the probability of both monozygotic twinsmonozygotic twins having ADHD was having ADHD was extremely high.extremely high.

o Sherman, McGue, and IaconoSherman, McGue, and Iacono found 67%found 67%

o Gilger, Pennington, and DeFries found 81%Gilger, Pennington, and DeFries found 81%

o Heffron, Martin, & Welsh found 100%Heffron, Martin, & Welsh found 100%

Dizygotic twins, on the other hand, were found Dizygotic twins, on the other hand, were found to have about the same chance as two, normal to have about the same chance as two, normal siblings - around 30 percentsiblings - around 30 percent

o In a study at the NIMH, multiple MRI In a study at the NIMH, multiple MRI snapshots were taken of children with ADHD snapshots were taken of children with ADHD throughout their life and compared with those throughout their life and compared with those who were not diagnosed with ADHD. who were not diagnosed with ADHD.

o The MRI’s showed that the ADHD child had a The MRI’s showed that the ADHD child had a brain that matured slower than the child brain that matured slower than the child without ADHD.without ADHD.

In a separate study at the NIMH, researchers In a separate study at the NIMH, researchers demonstrated a link between a person's ability to pay demonstrated a link between a person's ability to pay attention and the level of activity in the brain. attention and the level of activity in the brain. Subjects were asked to learn a list of words. As they Subjects were asked to learn a list of words. As they did, scientists used a PET scan (positron emission did, scientists used a PET scan (positron emission tomography) to take a look at the brain working. The tomography) to take a look at the brain working. The researchers measured the level of glucose used by the researchers measured the level of glucose used by the areas of the brain that inhibit impulses and control areas of the brain that inhibit impulses and control attention. The investigators found big differences attention. The investigators found big differences between people who have ADHD and those who between people who have ADHD and those who didn‘t. For people with ADHD, the brain areas that didn‘t. For people with ADHD, the brain areas that control attention used less glucose, indicating that control attention used less glucose, indicating that they were less active and thus cause inattention.they were less active and thus cause inattention.