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ADHD is a chronic behavioral disorder of childhood onset (by age seven). ADHD affects children, adolescents, and adults. It is characterized by behavior that is hyperactive, impulsive, or inattentive. There are several different types of ADHD. Some children are primarily inattentive and don't display signs of hyperactivity. Others, however, are hyperactive and/or impulsive. The rest exhibit a mixture of these symptoms.

The cause of ADHD is not known at this time, but brain chemistry, genetics, and environmental factors may all play roles in the development ADHD.

It is estimated that almost 8% of American children have ADHD (about 1-3 children in every classroom of 30 children). About 60% of children with ADHD will continue to experience trouble related to their disorder into adulthood.

Because so many cases of ADHD are diagnosed in childhood, the information provided here is geared toward children.


ADHD basics. American Academy of Pediatrics Healthy Children website. Available at: http://www.healthychildren.org/English/health-issues/conditions/adhd/Pages/ADHD-Basics.aspx. Accessed August 14, 2012.

Attention-deficit hyperactivity disorder (ADHD) in children. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php. Updated April 11, 2012. Accessed August 14, 2012.

Attention-deficit hyperactivity disorder (ADHD) in adults. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php. Updated April 25, 2012. Accessed August 14, 2012.

Attention-Deficit/Hyperactivity Disorder: Management. American Family Physician. Available at: http://familydoctor.org/familydoctor/en/diseases-conditions/attention-deficit-hyperactivity-disorder-adhd.html. Accessed August 14, 2012.

ADHD. The Nemours Foundation website. Available at: http://kidshealth.org/parent/medical/learning/adhd.html. Accessed August 14, 2012.

Attention deficit hyperactivity disorder (ADHD). National Institute of Mental Health website. Available at: http://www.nimh.nih.gov/health/publications/attention-deficit-hyperactivity-disorder/what-is-attention-deficit-hyperactivity-disorder.shtml. Accessed August 14, 2012.

Understanding ADHD. Children and Adults with Attention-Deficit/Hyperactivity Disorder website. Available at: http://www.chadd.org/AM/Template.cfm?Section=Causes. Accessed August 14, 2012.

Stern T, Rosenbaum J, Fava M, Biederman J, Rauch S. Massachusetts General Hospital Comprehensive Clinical Psychiatry. Philadelphia, PA: Mosby Elsevier; 2008.

Last reviewed September 2013 by Kari Kassir, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.