Several disorders may mimic or accompany attention-deficit disorder. ADHD exists alone in only about one-third of children. Many professionals object to the use of the single term "attention-deficit hyperactivity disorder" to encompass such a wide spectrum of behaviors, which they believe should be categorized into subgroups. Many of these problems require other modes of treatment and should be diagnosed separately, even if they accompany ADHD.
Attention-deficit disorder can appear without hyperactivity, in which case the child's primary symptoms are distractibility and an inability to persist in tasks.
About 14% of children diagnosed with ADHD also have oppositional-defiant disorder (ODD). The most common symptom for this disorder is a pattern of negative, defiant, and hostile behavior toward authority figures that lasts more than 6 months. In addition to displaying inattentive and impulsive behavior, these children demonstrate aggression, have frequent temper tantrums, and display antisocial behavior. A significant number of children with ODD also have anxiety disorders and depression, which should be treated separately. Many children who develop ODD at an early age go on to develop conduct disorder.
Some children with ADHD also have conduct disorder, which describes a complex group of behavioral and emotional disturbances seen in children. It includes aggression towards people and animals, destruction of property, deceitfulness, lying, or stealing, and general violation of rules.
Pervasive developmental disorder (PDD) is rare and usually marked by autistic-type behavior, hand-flapping, repetitive statements, slow social development, and speech and motor problems. If a child who has been diagnosed with ADHD does not respond to treatment, the parents might inquire about PDD, which often responds to antidepressants. Some children with PDD may also benefit from stimulants.
Children with ADHD often have difficulties with tasks that involve listening or hearing. Research is indicating that symptoms of the two disorders often overlap but may actually be two distinct disorders. Hearing problems themselves may cause ADHD symptoms.
Children diagnosed with attention-deficit disorder may also have bipolar disorder, formerly called manic depression. Indications of this problem include episodes of depression and mania (with symptoms of irritability, rapid speech, and disconnected thoughts), sometimes occurring at the same time. [For more information, see In-Depth Report #66: Bipolar disorder. ] Both disorders often cause inattention and distractibility and may be difficult to distinguish, particularly in children. Children with mania and ADHD may have more aggression, behavioral problems, and emotional disorders than those with ADHD alone. In some cases, ADHD in children or adolescents can be a marker for an emerging bipolar disorder. The primary way to differentiate bipolar disorder from ADHD is by the presence of a manic or hypomanic episode, which occurs in patients with bipolar disorder but not with ADHD. Most children with bipolar will also respond to the drug valproate, which does not typically work for ADHD in children.
Anxiety disorders commonly accompany ADHD. Obsessive-compulsive disorder is a specific anxiety disorder that shares many characteristics with ADHD and may share a genetic component. Young children who have experienced traumatic events, (including sexual or physical abuse or neglect), may exhibit characteristics of ADHD including impulsivity, emotional outbursts, and oppositional behavior.
Sleep disorders or disturbances are often associated with ADHD. Insomnia is common. In addition, specific sleep disorders -- restless legs syndrome and sleep apnea (sleep-disordered breathing) -- have been identified with hyperactivity and conduct disorder. [For more information, see In-Depth Reports #27: Insomnia; #95: Restless legs syndrome; #65: Sleep apnea.
Tourette Syndrome and Other Genetic Disorders. Several genetic disorders cause symptoms resembling ADHD, including fragile X and Tourette syndrome. Many patients with Tourette syndrome also have ADHD, and some of the treatments are similar.
Lead Poisoning. Children who ingest even small amounts of lead may manifest symptoms similar to those of ADHD. A child may be easily distractible, disorganized, and have trouble thinking logically. The major cause of lead toxicity is exposure to leaded paint, particularly in homes that are old and in poor repair.
Biederman J, Melmed RD, Patel A, McBurnett K, Konow J, Lyne A, et al. A randomized, double-blind, placebo-controlled study of guanfacine extended release in children and adolescents with attention-deficit/hyperactivity disorder. Pediatrics. 2008 Jan;121(1):e73-84.
Braun JM, Kahn RS, Froehlich T, Auinger P, Lanphear BP. Exposures to environmental toxicants and attention deficit hyperactivity disorder in U.S. children. Environ Health Perspect. 2006 Dec;114(12):1904-9.
Hamilton SS, Armando J. Oppositional defiant disorder. Am Fam Physician. 2008 Oct 1;78(7):861-6.
Heinrich H, Gevensleben H, Strehl U. Annotation: neurofeedback - train your brain to train behaviour. J Child Psychol Psychiatry. 2007 Jan;48(1):3-16.
Jensen PS, Arnold LE, Swanson JM, et al. 3-year follow-up of the NIMH MTA study. J Am Acad Child Adolesc Psychiatry. 2007 Aug;46(8):989-1002.
Millichap JG. Etiologic classification of attention-deficit/hyperactivity disorder. Pediatrics. 2008 Feb;121(2):e358-65.
Nigg JT, Breslau N. Prenatal smoking exposure, low birth weight, and disruptive behavior disorders. J Am Acad Child Adolesc Psychiatry. 2007 Mar;46(3):362-9.
Perrin JM, Friedman RA, Knilans TK; Black Box Working Group; Section on Cardiology and Cardiac Surgery. Cardiovascular monitoring and stimulant drugs for attention-deficit/hyperactivity disorder. Pediatrics. 2008 Aug;122(2):451-3.
Pliszka S; AACAP Work Group on Quality Issues. Practice parameter for the assessment and treatment of children and adolescents with attention-deficit/hyperactivity disorder. J Am Acad Child Adolesc Psychiatry. 2007 Jul;46(7):894-921.
Steiner H, Remsing L; Work Group on Quality Issues. Practice parameter for the assessment and treatment of children and adolescents with oppositional defiant disorder. J Am Acad Child Adolesc Psychiatry. 2007 Jan;46(1):126-41.
Swanson JM, Elliott GR, Greenhill LL, et al. Effects of stimulant medication on growth rates across 3 years in the MTA follow-up. J Am Acad Child Adolesc Psychiatry. 2007 Aug;46(8):1015-27.
Valera EM, Faraone SV, Murray KE, Seidman LJ. Meta-analysis of structural imaging findings in attention-deficit/hyperactivity disorder. Psychiatry. 2007 Jun 15;61(12):1361-9. Epub 2006 Sep 1.
Vetter VL, Elia J, Erickson C, Berger S, Blum N, Uzark K, et al. Cardiovascular monitoring of children and adolescents with heart disease receiving stimulant drugs: a scientific statement from the American Heart Association Council on Cardiovascular Disease in the Young Congenital Cardiac Defects Committee and the Council on Cardiovascular Nursing. Circulation. 2008 May 6;117(18):2407-23. Epub 2008 Apr 21.
Weber W, Vander Stoep A, McCarty RL, Weiss NS, Biederman J, McClellan J. Hypericum perforatum (St John's wort) for attention-deficit/hyperactivity disorder in children and adolescents: a randomized controlled trial. JAMA. 2008 Jun 11;299(22):2633-41.
Wilens TE, Upadhyaya HP. Impact of substance use disorder on ADHD and its treatment. J Clin Psychiatry. 2007 Aug;68(8):e20.
Williams JH, Ross L. Consequences of prenatal toxin exposure for mental health in children and adolescents: a systematic review. Eur Child Adolesc Psychiatry. 2007 Jun;16(4):243-53. Epub 2007 Jan 2.
© 2011 University of Maryland Medical Center (UMMC). All rights reserved.
UMMC is a member of the University of Maryland Medical System,
22 S. Greene Street, Baltimore, MD 21201. TDD: 1-800-735-2258 or 1.866.408.6885