Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Attention-Deficit/Hyperactivity Disorder


The Manual's Editorial Staff

Reviewed/Revised Sep 2023
Get the full details

What is attention-deficit/hyperactivity disorder?

Attention-deficit/hyperactivity disorder (ADHD) is a brain disorder that makes it hard to focus, pay attention, and sit still. It often causes problems at school and home.

ADHD symptoms can be mild or severe. Certain places (like school) can make them worse.

What causes ADHD?

Doctors aren't sure why a child gets ADHD. It's probably caused by problems with how the child's brain developed before birth. Less often, problems after birth cause ADHD.

ADHD is a brain problem and not just a behavior problem.

Children have a higher chance of having ADHD if they:

  • Have relatives with ADHD (it runs in families)

  • Weighed less than 3 pounds at birth

  • Had a head injury or brain infection

  • Were exposed to lead, alcohol, tobacco, or cocaine before birth

What are the symptoms of ADHD?

ADHD in children

Signs of ADHD in children:

  • Trouble paying attention

  • Extremely physically active

  • Very impulsive (do things without thinking)

Compared to adults, all children have a little trouble paying attention and sitting still. However, children who have ADHD have a lot more trouble than other children.

Signs of trouble paying attention:

  • Not listening when being talked to

  • Not following instructions or finishing tasks

  • Avoiding tasks that take a lot of thinking

  • Trouble organizing tasks

  • Being easily distracted

  • Losing or forgetting things

Signs of hyperactivity:

  • Fidgeting with hands or feet or moving legs

  • Getting out of their seat at school or at home

  • Running or climbing more than usual

  • Trouble playing quietly

  • Talking more than usual

Signs of being impulsive:

  • Shouting out answers before a question is done being asked

  • Trouble waiting for a turn

  • Talking when it isn’t their turn or interrupting others

Most children with ADHD become less hyperactive as they get older and are better able to cope. Most will grow up to be creative and productive adults. However, untreated ADHD can raise the chance of alcohol abuse, substance abuse, or suicide.

ADHD in adults

Signs of ADHD in adults:

  • Trouble concentrating

  • Difficulty completing tasks

  • Restlessness

  • Mood swings

  • Impatience

  • Difficulty in relationships

How can doctors tell if my child has ADHD?

How do doctors treat ADHD?

Yelling at or punishing your child doesn't help. Doctors will treat your child with:

  • Counseling on ways to improve behavior (behavioral therapy)

  • Medicine

Doctors and counselors can suggest things to help you and your child deal with ADHD. Things that often help include:

  • Having a set routine at home and school

  • Giving small rewards for good behavior

  • Being very consistent with what behavior you expect

  • Working with teachers to have shorter assignments and lessons in school

A child with ADHD may need special help at school. In the United States, the federal Individuals with Disabilities Education Act (IDEA) requires public schools to provide free and appropriate education to children with ADHD.

Medicines for ADHD are drugs such as Ritalin® and similar drugs that actually stimulate the brain. You might think your child is already too stimulated. However, these medicines stimulate the parts of the brain that help your child pay attention.

Stimulant drugs can have side effects like:

  • Not being able to sleep

  • Loss of appetite (children may eat so little they stop growing properly)

  • Fast heart rate and high blood pressure

To lessen the side effects, your doctor may suggest stopping medicine on weekends and during vacations from school.

Drugs Mentioned In This Article

Generic Name Select Brand Names
quiz link

Test your knowledge

Take a Quiz!