Attention-Deficit/Hyperactivity Disorder: Causes of ADHD

The exact cause of ADHD isn't known.

Experts do know that there are changes in the brains of people with the condition. ADHD is not caused by home or school situations or by poor parenting.

Here's what the experts know:

• Studies of the brain and its functioning show that children and adults who have ADHD are likely to have abnormal functioning (dysregulation) of certain neurotransmitters (chemicals in the brain), as well as in the nerve pathways that regulate behavior.
• There is a genetic link. ADHD tends to run in families. If one or both parents have ADHD, their children are more likely to develop the condition.
• Another factor that may play a role in causing ADHD is the presence of certain toxins in the environment, such as lead. Such toxins can interfere with the brain development of children exposed to them and possibly lead to ADHD.
• Studies show pregnant women who smoke or drink alcohol may have an increased risk of having a child with ADHD.

Research has shown that there is no evidence that ADHD is caused by:

• Eating too much sugar
• Allergies
• Immunizations

Reviewed by the doctors at The Cleveland Clinic Children's Hospital (2005).