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Understanding ADHD - When a Child Has Attention Deficit Hyperactivity Disorder What Happens in the Brain? The brain controls the body, thoughts, and feelings. It does so with the help of neurotransmitters. These chemicals help the brain send and receive messages. With ADHD, the level of these chemicals often varies. This may cause signs of ADHD to come and go. When Messages Are Not Received With ADHD, chemicals in certain parts of the brain can be in short supply. Because of this, some messages do not travel between nerve cells. Messages that signal a person to control behavior or pay attention aren't passed along. As a result, traits common to ADHD may occur. When brain chemicals are at low levels, messages can't cross gaps between nerve cells. When brain chemicals are at normal levels, messages can cross gaps between nerve cells. The parts of the brain shown in color can be affected by ADHD. Brain Functions Are Affected Each part of the brain controls certain behaviors and thought processes. ADHD is believed to affect more than one part of the brain. Depending on which brain site is involved, a child may show more symptoms of either attention deficit or hyperactivity disorder.

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