Other Disorders Associated with ADHD
Several disorders may mimic or accompany ADHD. Many of these conditions require other modes of treatment and should be diagnosed separately, even if they accompany ADHD.
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. It includes aggression towards people and animals, destruction of property, deceitfulness and lying, stealing, and general violation of rules.
Pervasive Developmental Disorder
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 stimulant medications.
Auditory Processing Disorder and Hearing Problems
Hearing problems may mimic ADHD symptoms and should be evaluated during diagnosis. Auditory processing disorder (APD) is another condition that can affect children’s ability to process spoken information. Children with ADP have normal hearing, but something in their brain prevents them from filtering out background noise and distinguishing between similar sounds. APD may be misdiagnosed as ADHD and the two conditions can also occur together.
Children diagnosed with attention-deficit disorder may also have bipolar disorder, formerly called manic depression. Bipolar disorder is marked by episodes of depression and mania (with symptoms of irritability, rapid speech, and disconnected thoughts),. Both disorders often cause inattention and distractibility and may be difficult to distinguish from one another, particularly in children. In some cases, ADHD in children or adolescents may be a marker for an emerging bipolar disorder. [For more information, see In-Depth Report #66: Bipolar disorder. ]
Anxiety disorders often 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. [For more information, see In-Depth Report #28: Anxiety Disorders.]
Sleep disorders or disturbances are often associated with ADHD. Insomnia is common -- as are restless legs syndrome and sleep apnea (sleep-disordered breathing. [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.
Review Date: 01/27/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.