ADHD---Demographics--etc

Demographics

ADHD is a common childhood disorder. It is estimated to affect 3–7% of all children in the United States, representing up to two million children. The percent in fact be even higher, with up to 15% of boys in grades one through five being afflicted. On average, at least one child in each public and private classroom in the United States has ADHD. In countries such as Canada, New Zealand, and Germany, the prevalence rates are estimated to be 5–10% of the population.

The traditional view of ADHD is that boys are affected more often than girls. Community-based samples have found an incidence rate in boys that is double that of girls. In fact, statistics gathered from patient populations have reported male-to-female ratios of up to 4:1. However, as the understanding of ADHD has grown since the early 1990s and as the symptoms have been better recognized, the actual number of females who are affected by ADHD may be more similar to males than previously thought.

Causes and symptoms

The cause of ADHD is unknown. However, evidence is consistent with a biological cause rather than an environmental cause (e.g., home life). Not all children from dysfunctional homes or families have ADHD.

For many years, it was thought that ADHD developed following a physical blow to the head, or from an early childhood infection, leading to the terms "minimum brain damage" and "minimum brain dysfunction." However, these definitions apply to only a very small number of people diagnosed with ADHD, and so have been rejected as the main cause.

Another once-favored theory was that eating refined sugar or chemical additives in food produced hyperactivity and inattention. While sugar can produce changes in behavior, evidence does not support this proposed association. Indeed, in 1982, the results presented at a conference sponsored by the U.S. National Institutes of Health conclusively demonstrated that a sugar- and additive-restricted diet only benefits about 5% of children with ADHD, mostly young children and those with food allergies.

The biological roots of ADHD may involve certain areas of the brain, specifically the frontal cortex and nearby regions. One explanation is that the executive functions are controlled by the frontal lobes of the brain. Magnetic resonance imaging (MRI) examination of subjects who are exposed to a sensory cue has identified decreased activity of regions of the brain that are involved in tasks that require attention. Another MRI-based study published in November 2003 also implicates a region of the brain that controls impulsive behavior. Finally, a study conducted by the U.S. National Institute of Mental Health (NIMH) documented that the brains of children and adolescents with ADHD are 3–4% smaller than those of their ADHD-free counterparts. Additionally, the decreased brain size is not due to the use of drugs in ADHD treatment, the researchers concluded in a paper published in October 2002.

ADHD symptoms can sometimes be relieved by the use of stimulants that increase a chemical called dopamine. This chemical functions in the transmission of impulses from one neuron to another. Too little dopamine can produce decreased motivation and alertness. These observations led to the popular "dopamine hypothesis" for ADHD, which proposed that ADHD results from the inadequate supply of dopamine in the central nervous system.

The observations that ADHD runs in families (10–35% of children with ADHD have a direct relative with the disorder) point to an underlying genetic origin. Studies with twins have shown that the occurrence of ADHD in one twin is more likely to be mirrored in an identical twin (who has the same genetic make-up) than in a fraternal twin (whose genetic make-up is similar but not identical).

The genetic studies have implicated the binding, transport, and enzymatic conversion of dopamine. Two genes in particular have been implicated: a dopamine receptor (DRD) gene on chromosome 11 and the dopamine transporter gene (DAT1) on chromosome 5.

There may be environmental factors that influence the development of ADHD. Complications during pregnancy and birth, excessive use of marijuana, cocaine, and/or alcohol (especially by pregnant women), ingestion of lead-based paint, family or marital tension, and poverty have been associated with ADHD in some people. However, many other ADHD sufferers do not display any of these associations.

Heavy use of alcohol by a pregnant woman can lead to malformation of developing nerve cells in the fetus, which can result in a baby of lower than normal birth weight with impaired intelligence. This condition, called fetal alcohol syndrome, can also be evident as ADHD-like hyperactivity, inattention, and impulsive behavior.

Diagnosis

ADHD is sometimes difficult to diagnose. Unlike the flu or a limb fracture, ADHD lacks symptoms that can be detected in a physical examination or via a chemical test. Rather, the diagnosis of ADHD relies on the presence of a number of characteristic behaviors over an extended period of time. Often the specialist will observe the child during high-stimuli periods such as a birthday party and during quieter periods of focused concentration. Diagnosis uses the DSM-IV criteria, originally published in 1994, in combination with an interview and assessment of daily activity by a qualified clinician. (As of December 20ised DSM criteria are pending. These revisions will reflect the increased awareness of the greater-than-perceived prevalence of ADHD in girls and women.)

The benchmarks for either inattention or for hyperactivity/impulsive behavior must be met. These benchmarks typically occur by the age of seven and are not exclusive to one particular social setting such as school. These benchmarks must have been present for an extended period of time, at least six months or more. There are nine separate criteria for each category. For diagnosis, six of the nine criteria must be met. Examples of diagnostic signs of inattention include difficulty in maintaining concentration on a task, failure to follow instructions, difficulty in organizing approaches to tasks, repeated misplacement of tools necessary for tasks, and tendency to become easily distracted. Examples of hyperactivity or impulsive behavior include fidgeting with hands or feet, restlessness, difficulty in being able to play quietly, excessive talk, and tendency to verbally or physically interrupt.

Because ADHD can be associated with the use of certain medications or supplements, diagnosis involves screening for the past or present use of medications such as anticonvulsant or antihypertensive agents, and caffeinecontaining drugs.

Diagnosis of ADHD can also be complicated by the simultaneous presence of another illness. Diagnosis involves screening for bipolar disorder, depression, eating disorder, learning disability, panic disorder (including agoraphobia), sleep disorder, substance abuse, or Tourette's syndrome. Almost half of all children (mostly boys) with ADHD display what has been termed "oppositional defiant behavior." These children tend to be stubborn, temperamental, belligerent, and can lash out at others over a minor provocation. Without intervention, such children could progress to more serious difficulties such as destruction of property, theft, arson, and unsafe driving.

Other, nonclinical information such as legal infractions (arrests, tickets, vehicle accidents), school reports, and interviews with family members can be valuable, as ADHD can be perceived as antisocial, erratic, or uncommon behavior.

A complete physical examination is recommended as part of the diagnosis. The examination offers the clinician an opportunity to observe the behavior of the person. More specific tests can also be performed. Children can be assessed using the Conner's Parent and Teacher Rating Scale. Adolescent and adult assessment can utilize the Brown Attention Deficit Disorder Scale. Impulsive and inattentive behavior can be assessed using the Conner's Continuous Performance Test (CPT) or the Integrated Visual and Auditory CPT. Girls can be specifically assessed using the Nadeau/Quinn/Littman ADHD Self-Rating Scale.