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Attention-Deficit/Hyperactivity Disorder (ADHD)

Causes And Symptoms

The causes of ADHD are not known. However, it appears that heredity plays a major role in the development of ADHD, with many researchers assuming that ADHD is due to a genetic defect that results in altered brain biochemistry. Children with an ADHD parent or sibling are more likely to develop the disorder themselves. Before birth, ADHD children may have been exposed to poor maternal nutrition, viral infections, or maternal substance abuse. In early childhood, exposure to lead or other toxins can cause ADHD-like symptoms. Traumatic brain injury or neurological disorders may also trigger ADHD symptoms. Although the exact cause of ADHD is not known, an imbalance of certain neurotransmitters, the chemicals in the brain that transmit messages between nerve cells, is believed to be the mechanism behind ADHD symptoms. In 1990, a study by researchers at the National Institute for Mental Health documented the neurobiological effects of ADHD through brain imaging. The results showed that the rate at which the brain uses glucose, its main energy source, was shown to be lower in persons with ADHD, especially in the portion of the brain that is responsible for attention, handwriting, motor control and inhibition responses.

A widely publicized study conducted in the early 1970s suggested that allergies to certain foods and food additives caused the characteristic hyperactivity of ADHD children. Although some children may have adverse reactions to certain foods that can affect their behavior (for example, a rash might temporarily cause a child to be distracted from other tasks), carefully controlled follow-up studies have uncovered no link between food allergies and ADHD. Another popularly held misconception about food and ADHD is that the consumption of sugar causes hyperactive behavior. Again, studies have shown no link between sugar intake and ADHD. It is important to note, however, that a nutritionally balanced diet is important for normal development in all children.

Diagnosis is based on a collaborative process that involves affected children, psychiatrists or other physicians, the child's family and school. Deciding what treatment will best benefit the affected child requires a careful diagnostic assessment after a comprehensive evaluation of psychiatric, social, cognitive, educational, family and medical/neurological factors. A thorough evaluation can take several hours and may require more than one visit to a physician. Treatment follows only after the evaluation is made.

Psychologists and other mental health professionals typically use the criteria listed in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) as a guideline for determining the presence of ADHD. For a diagnosis of ADHD, DSM-IVTR requires the presence of at least six of the following symptoms of inattention, or six or more symptoms of hyperactivity and impulsivity combined:


  • Fails to pay close attention to detail or makes careless mistakes in schoolwork or other activities.
  • Has difficulty sustaining attention in tasks or activities.
  • Does not appear to listen when spoken to.
  • Does not follow through on instructions and does not finish tasks.
  • Has difficulty organizing tasks and activities.
  • Avoids or dislikes tasks that require sustained mental effort (e.g., homework).
  • Is easily distracted.
  • Is forgetful in daily activities.


  • Fidgets with hands or feet or squirms in seat.
  • Does not remain seated when expected to.
  • Runs or climbs excessively when inappropriate (in adolescence and adults, feelings of restlessness).
  • Has difficulty playing quietly.
  • Is constantly on the move.
  • Talks excessively.


  • Blurts out answers before the question has been completed.
  • Has difficulty waiting for his or her turn.
  • Interrupts and/or intrudes on others.

DSM-IV-TR also 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. Children who meet the symptom criteria for inattention, but not for hyperactivity/impulsivity are diagnosed with attention-deficit/hyperactivity disorder, predominantly inattentive type, commonly called ADD. (Young girls with ADHD may not be diagnosed because they have mainly this subtype of the disorder.)

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