Cause

The exact cause of attention deficit hyperactivity disorder (ADHD) isn't known. But it may run in families. Ongoing research is focused on finding the genes that cause a person to be likely to get ADHD.

A mother's use of cigarettes, alcohol, or other drugs during pregnancy may increase the risk for ADHD. Also, exposure to lead may cause symptoms linked with ADHD.¹

Although many parents believe that foods with sugar and food additives make their children more hyperactive, these foods haven't been shown to cause ADHD.²

Symptoms

The three types of ADHD symptoms include:

• Trouble paying attention (inattention). People with ADHD are easily distracted. They have a hard time focusing on any one task.
• Trouble sitting still for even a short time (hyperactivity). Children with ADHD may squirm, fidget, or run around at the wrong times. Teens and adults often feel restless and fidgety. They aren't able to enjoy reading or other quiet activities.
• Acting before thinking (impulsivity). People with ADHD may talk too loud, laugh too loud, or become angrier than the situation calls for. Children may not be able to wait for their turn or to share. This makes it hard for them to play with other children. Teens and adults may make quick decisions that have a long-term impact on their lives. They may spend too much money or change jobs often.

These symptoms affect all people who have ADHD. But typical behavior varies by age.

• In preschool-age children, symptoms are often the same as normal behavior for young children.
• In children between the ages of 6 and 12, signs of ADHD are more obvious than in other age groups.
• In teens between the ages of 13 and 18, problems that began in earlier years may continue or get worse.
• Symptoms of ADHD in adults may not be as noticeable as in other age groups.