The brain and central nervous system work like a command center to coordinate every system in the human body. Comprised of millions of nerve cells, the command center receives and transmits signals from one part of the body to another.

Impulses are carried along the length of nerve cells and “jump” from one cell to another. The gap between nerve cells is called a synapse. The chemical messengers that carry the impulse across the gap are called neurotransmitters.

Meet Your Neurotransmitters

Epinephrine and norepinephrine are two neurotransmitters that mobilize the body's reaction to danger and trigger the “fight or flight” response you've probably experienced as a racing heart and heightened senses. Dopamine is a neurotransmitter that helps regulate your general activity level, whether you're active or passive, alert or disinterested, or awake or asleep.

Studies on Neurotransmitters

Many studies have shown a link between ADHD and an imbalance of neurotransmitters in the brain. Stimulant drugs used to treat ADHD relieve symptoms by increasing dopamine levels in the brain. Using indirect drug response research, researchers have discovered that insufficient levels of dopamine may be associated with ADHD.

Other studies associated ADHD with an imbalance of norepi-nephrine and dopamine in the brain. Having too much norepi-nephrine could make you feel agitated and in a constant state of fight or flight, a common symptom in adults with ADHD. Although scientists haven't yet pinpointed the exact mechanism that causes ADHD, they have discounted many older theories and are conducting promising research that suggests the disorder is caused by an imbalance of neurotransmitters in the brain.

If the condition proves to be not one but several different disorders, researchers may be able to isolate specific causes and treat them separately. The good news is that if you have adult ADHD, medical science is closer than ever to discovering the root causes behind it.