Other Disorders Associated with ADHD:

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 without Hyperactivity

Attention-deficit disorder can appear without hyperactivity, in which case the child's primary symptoms are distractibility and an inability to persist in tasks.

Oppositional-Defiant Disorder

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.

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

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.

Central Auditory Processing Disorder and Hearing Problems

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.

Bipolar Disorder (Manic Depression)

Children diagnosed with attention-deficit disorder may also have bipolar disorder, commonly 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 even 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

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, exhibit characteristics of ADHD, including impulsivity, emotional outbursts, and oppositional behavior.

Sleep Disorders

Sleep disorders or disturbances are very common with ADHD patients. Insomnia is common. In addition, specific sleep disorders -- restless legs syndrome and sleep-disordered breathing -- have been identified with hyperactivity and conduct disorder.

Restless Legs Syndrome (RLS). Some experts believe RLS and periodic limb movement disorder are strongly associated with ADHD in some children. One theory is that the two are linked by a common mechanism. The disorders have much in common, including poor sleep habits, twitching, and the need to get up suddenly and walk about frequently. They may even be genetically linked. For example, both have been associated with lower levels of dopamine in the brain, which is associated with faulty motor control, a common problem in both disorders.

Sleep-Disorder Breathing and Sleep Apnea. Some research has shown an association between mild symptoms of ADHD and sleep-disordered breathing, including snoring and obstructive sleep apnea in children and adults. Treating the sleep-related breathing disorders may improve the attention disorder in some children. (One study indicated that such problems are unlikely to be associated with children with moderate to severe ADHD.) [For more information, see In-Depth Report #65: Sleep apnea.]

Other Diagnoses

Tourette Syndrome and Other Genetic Disorders. Several genetic disorders cause symptoms resembling ADHD, including fragile X and Tourette syndrome. About 50% of those with Tourette syndrome also have ADHD, and some of the treatments are similar.

Other Medical Conditions. A number of medical conditions, including hyperthyroidism and vision problems, can produce ADHD-like symptoms.

Lead. Children who ingest even low 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.