Attention Deficit Hyperactivity Disorder
(ADHD) (ADD)
Medical Author: Dennis S. Phillips, MD, and John Mersch, MD, FAAP
Medical Editor: William C. Shiel Jr., MD, FACP, FACR
What is attention deficit hyperactivity disorder (ADHD)?
ADHD refers to a chronic biobehavioral disorder that initially manifests in childhood and
is characterized by hyperactivity, impulsivity, and/or inattention. Not all of
those affected by ADHD manifest all three behavioral categories. These symptoms
can lead to difficulty in academic, emotional, and social functioning. The
diagnosis is established by satisfying specific criteria and may be associated
with other neurological, significant behavioral, and/or developmental/learning
disabilities. Therapy may consider the use of medication, behavioral therapy, and
adjustments in day-to-day lifestyle activities.
Studies in the United States indicates approximately 8%-10% of
children satisfy diagnostic criteria for ADHD. ADHD is, therefore, one of the
most common disorders of childhood. ADHD occurs two to four times more commonly
in boys than girls (male to female ratio 4:1 for the predominantly hyperactive
type vs. 2:1 for the predominantly inattentive type). Three subtypes of ADHD are described: (1) predominantly inattentive, (2) predominantly hyperactive and impulsive, and (3) combined. While previously believed to be "outgrown" by adulthood, current opinion indicates that many children will continue throughout life with symptoms that may affect both occupational and social functioning. Some medical researchers note that approximately 40%-50% of ADHD-hyperactive children will have (typically non-hyperactive) symptoms persist into adulthood.
What is the cause of ADHD?
The cause of ADHD has not been fully defined. One theory springs from observations in functional brain imagining studies between those with and without symptoms. Similar variations have been shown in studies of the structure of the brain of affected and non-affected individuals. Animal studies have demonstrated differences in the chemistry of brain transmitters involved with judgment, impulse control, alertness, planning, and mental flexibility.
A genetic predisposition has been demonstrated in (identical) twin and sibling studies. If one identical twin is diagnosed with ADHD, there is at 92% probability of diagnosis with the twin sibling. When comparing nonidentical twin sibling subjects, the probability falls to 33%. (Overall population incidence is 8%-10% in the U.S., as described above.)
What are the symptoms of ADHD?
The diagnostic criteria for ADHD are outlined in the Diagnostic and Statistical Manual of Mental Health,
4th ed. (DSM-IV). All of the symptoms of inattention, hyperactivity, and impulsivity must have persisted for at least
six months to a degree that is maladaptive and inconsistent with the developmental level of the child.
Inattention:
- The child often fails to give close attention to details or makes careless mistakes in schoolwork, work, or other activities.
- The child often has difficulty sustaining attention in tasks or play activities.
- The child often does not seem to listen when spoken to directly.
- The child often does not follow through on instructions and fails to finish schoolwork, chores, or duties in the workplace (not due to oppositional behavior or failure to understand instructions).
- The child often has difficulty organizing tasks and activities.
- The child often avoids, dislikes, or is reluctant to engage in tasks that require sustained mental effort (such as schoolwork or homework).
- The child often loses things necessary for tasks or activities (toys, school assignments, pencils, books, or tools).
- The child is often easily distracted by extraneous stimuli.
- The child is often forgetful in daily activities.
Hyperactivity:
- The child often fidgets with his/her hands or feet or squirms in his/her seat
.
- The child often leaves his/her seat in the classroom or in other situations in which remaining seated is expected.
- The child often runs about or climbs excessively in situations in which it is inappropriate.
- The child often has difficulty playing or engaging in leisure activities quietly
.
- The child often talks excessively.
Impulsivity:
- The child often blurts out answers before questions have been completed.
- The child often has difficulty awaiting his/her turn
.
- The child often interrupts or intrudes on others (for example, butts into conversations or games).
DSM-IV criteria for diagnosis of ADHD requires that some hyperactive, impulsive, or inattention symptoms that cause present difficulties were present before 7 years of age and are present in two or more settings (at school [or work] or at home). Similarly, there must be clear evidence of significant impairment in social, academic, or occupational functioning. In addition, symptoms may not entirely be caused by another severe physical disorder (for example, severe illness associated with chronic pain) or mental disorder (for
example, schizophrenia, other psychotic disorders, severe disabling mood disorders, etc.).
Inattention symptoms are most likely to manifest about at 8 to 9 years of age and
commonly are lifelong. The "delay" in onset of inattentive symptoms may reflect
its more subtle nature (vs. hyperactivity) and/or variability in the maturation
of cognitive development. Hyperactivity symptoms are usually obvious by 5 years
of age and peak in severity between 7 to 8 years of age. With maturation, these
behaviors progressively decline and often have been "outgrown" by adolescence.
Impulsive behaviors are commonly linked to hyperactivity and also peak about 7
to 8 years of age; however, unlike their hyperactive counterpart, impulsivity
issues remain well into adulthood. Impulsive adolescents are more likely to
experiment with high-risk behaviors (drugs, sexual, driving, etc.). Impulsive
adults have a higher rate of financial mismanagement (impulse buying, gambling,
etc.).
Next: How is ADHD diagnosed? »
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