Attention-deficit/hyperactivity disorder (AD/HD) is a neurobiological disorder characterized by hyperactivity, impulsive behavior, and the inability to remain focused on tasks or activities.
AD/HD, also known as hyperkinetic disorder (HKD) outside of the United States, is estimated to affect 3–7 percent of school-aged children, and seems to afflict boys more often than girls. However, the prevalence in boys may be cited because often girls are not diagnosed until later in age. Although difficult to assess in infancy and toddlerhood, signs of AD/HD may begin to appear as early as age two or three, but visible symptoms change as adolescence approaches. Many symptoms, particularly hyperactivity, diminish in early adulthood, while impulsivity and inattention problems often continue.
First documented in 1902, AD/HD has been called minimal brain dysfunction, hyperkinetic reaction, and attention-deficit disorder (ADD). The name AD/HD reflects the various behaviors of inattention, hyperactivity, and impulsiveness that characterize the disorder. Its more precise classification is a result of the Diagnostic and Statistical Manual, fourth edition (DSM-IV) system for characterizing and diagnosing mental and behavioral disorders.
Children with AD/HD have difficulties with inattention that can be manifest as a lack of concentration, an easily distracted focus, and an inability to know when and how long to focus. The characteristics of inattention vary with each AD/HD child; however, all most often translate into poor grades and difficulties in school and other social arenas. AD/HD children act impulsively, taking action first and thinking later. They are constantly moving, running, climbing, squirming, and fidgeting. Yet, they often have trouble with gross and fine motor skills and, as a result, they may be physically clumsy and awkward. Their clumsiness may also extend to their social skills. They are sometimes shunned by peers due to their impulsive and intrusive behavior.
Of the 3–7 percent of school-aged children with AD/HD, some will have a reduction of symptoms as they reach adulthood. However, 65 percent of AD/HD children will continue to display characteristics of AD/HD through adulthood. Until recently, it was believed that boys were three times more likely to have AD/HD; however, that gap has been narrowed. It is more likely that the presence of AD/HD is distributed equally between boys and girls. The reason for the discrepancy was, in part, because young boys tend to more readily and overtly manifest the characteristics of AD/HD, making diagnosis easier. In addition, the inattentive form affects girls more than the hyperactive form; as a result, girls may be less likely to be diagnosed.
Causes and symptoms
The causes of AD/HD are not specifically known. However, it is a neurologically based disease that may be genetic. Children with an AD/HD parent or sibling are more likely to develop the disorder themselves. Although the exact cause of AD/HD is not known, an imbalance or deficiency of certain neurotransmitters—the chemicals in the brain that transmit messages between nerve cells—is believed to be the mechanism behind AD/HD symptoms.
A widely publicized study conducted by Dr. Ben Feingold in the early 1970s suggested that allergies to certain foods and food additives caused the characteristic hyperactivity of AD/HD children. By eliminating the food allergen, the premise was that AD/HD characteristics would disappear. Although some children may have adverse reactions to certain foods and food additives that can affect their behavior, carefully controlled follow-up studies have uncovered no link between food allergies and AD/HD. Another popularly held misconception about food and AD/HD is that the consumption of sugar causes the hyperactive behavior in an AD/HD child. Again, studies have shown no link between sugar intake and AD/HD. (In a recent study conducted by the National Institute of Mental Health, the level of glucose use in the brain was actually lower in individuals with AD/HD. Since glucose is the main source of fuel for the brain, this is a significant finding.) Finally, parenting style is not a cause for AD/HD. While certain parenting skills and/or deficiencies can affect the environment of an AD/HD child and, as a result, exasperate or help manage the characteristics of AD/HD, it appears that neurological issues are the primary causal agents at play.
In order to diagnose AD/HD, psychologists and other mental health professionals typically use the criteria listed in the DSM-IV. DSM-IV requires the presence of at least six of the following symptoms of inattention, or six or more symptoms of hyperactivity and impulsivity combined.
Of those symptoms, AD/HD can be categorized further by three subtypes. Each subtype exhibits particular behaviors that make up the general symptoms of a child with AD/HD. They are:
AD/HD predominantly inattentive type (AD/HD-I)
AD/HD predominantly hyperactive-impulsive type (AD/HD-HI)
AD/HD combined type (AD/HD-C) is a combination of the symptoms exhibited by the other two subtypes (inattentive type and hyperactive-impulsive type). Also, for a complete diagnosis, DSM-IV requires that some symptoms develop before age seven, and that they significantly impair functioning in two or more settings (e.g., home and school) for a period of at least six months.
Symptoms may include:
AD/HD cannot be diagnosed with a laboratory test. Diagnosis is difficult and it takes into consideration many aspects of the child's behavior. Often the child's teacher is the one to bring the first signs to the attention of the parents. However, the first step in determining if a child has AD/HD is to consult with a pediatrician. The pediatrician can make an initial evaluation of the child's developmental maturity compared to other children in his or her age group. The physician should also perform a comprehensive physical examination to rule out any organic causes of AD/HD symptoms, such as an overactive thyroid or vision or hearing problems.
If no organic problem can be found, a psychologist, psychiatrist, neurologist, neuropsychologist, or learning specialist is typically consulted to perform a comprehensive AD/HD assessment. A complete medical, family, social, psychiatric, and educational history is compiled from existing medical and school records and from interviews with parents and teachers. Interviews may also be conducted with the child, depending on his or her age. Along with these interviews, several clinical inventories may also be used, such as the Conners' Rating Scales (Teacher's Questionnaire and Parent's Questionnaire), Child Behavior Checklist (CBCL), and the Achenbach Child Behavior Rating Scales. These inventories provide valuable information on the child's behavior in different settings and situations.
Other disorders such as depression, anxiety disorder, and learning disorders can cause symptoms similar to AD/HD. A complete and comprehensive psychiatric assessment is critical to differentiate AD/HD from other possible mood and behavioral disorders. Bipolar disorder, for example, may be misdiagnosed as AD/HD.
Public schools are required by federal law to offer free AD/HD testing upon request. A pediatrician can also provide a referral to a psychologist or pediatric specialist for AD/HD assessment. Parents should check with their insurance plans to see if these services are covered.