Information Section: Conditions
Condition: ADHD
Article: Attention Deficit Hyperactivity Disorder Overview
Source: Leslie E. Packer, PhD
File Last Revised: January 20, 2005

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OUR CHANGING CONCEPTUALIZATION OF ADHD

One of the most common childhood-onset conditions is Attention Deficit Hyperactivity Disorder (ADHD). Estimates of the prevalence of ADHD range from 3% to 7% of children.

Over the years, our understanding of ADHD has changed considerably. At different points within the last 100 years, ADHD was viewed as "minimal brain dysfunction" or a "hyperkinetic disorder of childhood."  Such terminology reflected the emphasis on a neurological basis for the hyperactivity exhibited by these children. Over the past decades, the emphasis has shifted to emphasizing both the inattention and hyperactivity-impulsivity components. At the present time, clinicians talk about three different subtypes of ADHD: (1) children who are primarily inattentive, (2) children whose main problem is impulsivity-hyperactivity, and (3) children who have both inattention and impulsivity-hyperactivity problems to a significant degree (the combined subtype).  

When reading about ADHD, it may be helpful to note whether an author is talking about "ADHD" or a specific subtype of ADHD because there are differences associated with the different subtypes of ADHD in terms of the types of deficits or challenges the child faces and in terms of long-term prognosis. 

A PICTURE SPEAKS 1,000 WORDS

Many people erroneously assume that if the child is hyperactive, the brain must also be overactive. This is not the case, however, as this brain scan from the research of Dr. Zametkin (1990) shows. In the image, high levels of activity are indicated by red, orange, and yellow, while lower levels of activity are indicated by greens and blues. When given a problem to think about, the "normal" control shows a pattern of activity in the brain, but the brain of the individual with ADHD is not as active.  

It may be helpful to think of ADHD as "the lights are off," because it is the underactivity in the "braking" systems in the brain that leads to overactive behavior, impulsivity, and/or inability to sustain attention. Another way to think about ADHD is in terms of "response disinhibition" or more informally, "the lights are off" -- that there is less of an ability to inhibit responding, leading to impulsivity, hyperactivity, and difficulty stopping oneself from being distracted.  

Do such data show that ADHD is strictly a biological problem?  Although a growing body of research suggests that the brains of children with ADHD differ from the brains of non-ADHD in terms of the size of some of the structures in the brain and in terms of neurochemical levels and activity in the brain and that these differences are may be due to genetic factors and other biological factors such as prenatal and postnatal factors, ADHD also appears to be influenced by environmental factors such as home environment and classroom structure.

DIAGNOSING ADHD

ADHD is characterized by either inattention and/or hyperactivity-impulsivity. There is a veritable "Chinese menu" for determining whether a particular patient meets the diagnostic criteria for ADHD, and if so, for which subtype. As a result, two individuals could both be diagnosed with ADHD and yet have significantly different features or challenges.  

In the United States, mental health professionals use the DSM-IV diagnostic criteria* while in Europe, mental health professional generally use the ICD-10 diagnostic criteria.  

Note that in the American criteria, a child need not have both hyperactivity-impulsivity and inattention. It is possible to be diagnosed if inattention is the primary or sole problem. Although many children and teenagers will meet criteria for both inattention and hyperactivity-impulsivity (i.e., they will meet diagnostic criteria for the "combined" subtype), keeping the different subtypes (primarily inattentive, primarily hyperactive-impulsive, or combined) is helpful.  

The diagnostic criteria include other conditions that must be ruled out before a diagnosis of ADHD is made. Because there are many other possible explanations for inattentive or hyperactive-impulsive behavior, and as part of the diagnostic examination, the professional needs to collect information from multiple sources of information. Some of the other conditions that produce behavior patterns or symptoms that might at first blush appear to be ADHD include: 

  • A learning disability that leads to poor performance in school, frustration, and a behavior pattern where the child seems to stop paying attention or "gives up" listening to the teacher;
  • Attention lapses caused by petit mal seizures;
  • Attention lapses caused by obsessive thoughts or silent compulsive rituals;
  • A middle ear infection causing an intermittent hearing problem that interferes with the child's ability to respond to orally presented requests or material;
  • Disruptive or unresponsive behavior due to anxiety, depression, or bipolar disorder (manic phase).
  • Environmental factors or stressors that lead to restlessness or inattention (such as divorce, problems on the job, etc.) 

Not surprisingly, many sources on ADHD do not list another differential diagnosis that I would include:  giftedness. On this web site, you will find several articles about differentiating between ADHD and giftedness. Although it is certainly possible that some children and teenagers have both ADHD and giftedness, Dr. Webb and others point out that in some cases, gifted children are being misunderstood -- and misdiagnosed -- as having ADHD. 

In another section on this site, a condition known as Executive Dysfunction is described. If you've already read about it, you may have noted that many of the symptoms described sound remarkably like the inattentive criteria in the DSM-IV criteria for ADHD. Specifically, the following signs or symptoms of "inattention" may also indicate executive dysfunction: 

  • Often fails to give close attention to details or makes careless mistakes in schoolwork, work, or other activities;
  • Often has difficulty sustaining attention in tasks or play activities;
  • 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);
  • Often has difficulty organizing tasks and activities;
  • Often avoids, dislikes, or is reluctant to engage in tasks that require sustained mental effort (such as schoolwork or homework);
  • Often loses things necessary for tasks or activities (e.g., toys, school assignments, pencils, books, or tools);
  • Is often easily distracted by extraneous stimuli 

In order to clarify diagnostic issues, a neuropsychological assessment may be helpful or necessary.

GENDER DIFFERENCES

ADHD seems to be more prevalent in boys than girls for the hyperactive-impulsive subtype and for the combined subtype. The gender difference is less in the inattentive subtype. Dr. Joseph Biederman and his colleagues compared boys and girls with ADHD to boys and girls without ADHD. They found that girls with ADHD were more likely than boys to have predominantly inattentive subtype of ADHD. When compared to boys with ADHD, girls with ADHD were less likely to have a learning disability and less likely to experience problems in school or outside of school. Girls with ADHD were also less likely to have depression, conduct disorder, or oppositional defiant disorder. In light of these data, the investigators suggested that there might be a gender bias in terms of referring children for assessment or treatment, with girls being less likely to be referred. 

In an analysis of other studies on ADHD, Gershon (2002) looked at gender differences in ADHD. Gershon's analysis indicated that when compared to ADHD boys, ADHD girls had lower ratings on hyperactivity, inattention, impulsivity, and externalizing problems, and had greater intellectual impairment and more internalizing problems than boys with ADHD. 

One of the more intriguing findings has been the relationship between inattention-impulsivity, early peer relationships, and the emergence of conduct disorder. Snyder, Prichard, et al. (2004) found that with boys, the inattention-impulsivity was related to conduct problems but the relationship was mediated or modulated, in part, by peer rejection and involvement in coercive exchanges with peers. For girls, the relationship between inattention-impulsivity and conduct disorder was not as clearly mediated by peer interactions, although peer difficulties did affect the emergence of conduct problems. Their study not only elucidates the complex relationship between gender, inattention-impulsivity, peer difficulties, and conduct disorder, but it suggests that we need earlier interventions to address any emerging peer difficulties.

WHAT CONDITIONS ARE ASSOCIATED WITH ADHD?

When two conditions occur together in the same individual, we say they are "comorbid."  If the two conditions tend to occur together more often than would be expected by chance in the population, we say that the conditions are "associated" (with each other).

Certain conditions tend to occur in children and teens with ADHD more than you would expect to see by chance, and some sources have estimated that approximately 2/3 of children with ADHD will have one or more comorbid conditions during their lifetime. In clinical settings, the comorbid conditions most commonly reported in ADHD are:

 In adults with ADHD seen in clinical settings, Antisocial Personality Disorder, substance abuse, learning disabilities, and mood disorders are often comorbid with the ADHD. Other personality disorders are also more common in adults with ADHD:  histrionic, passive-aggressive, and borderline personality disorders. 

Over the years, I have occasionally encountered references to a possible connection between ADHD and visual problems. The deficits in smooth tracking and pursuit have been hypothesized to help explain certain reading disabilities and even some behavioral issues. The research in this area, however, is inadequate to draw any unequivocal conclusions, and in 2001, one of the professional pediatrics organizations identified vision therapy as an unproven modality for children with ADHD.  That said, new research suggests that a computerized eye tracking test may accurately identify 93% of children with ADHD who have been diagnosed by clinical history and reports. The researchers report that the test measure also seems to correlate with those who respond well to Ritalin, and hope that their procedure can ultimately used not only as a tool in diagnosis, but to help predict which children are likely to respond well to medication.

That said, even when visual acuity is normal, I have, on occasion, referred some children or teens with ADHD for optometric or ophthalmological examination to determine if oculomotor problems were contributing to learning disabilities as my observations of the children or teens while they were reading suggested visual deficits that were affecting them.

ADHD: OUTCOMES AND PROGNOSIS

Up to 85% of children with ADHD may continue to have problems in adolescence. Peer problems that are noted in childhood may persist, and if the ADHD symptoms also persist into adolescence, the peer impact is even more significant. Adolescents who have a history of ADHD in their childhood may be more likely to have fewer friends, experience greater peer rejection, and have friends who are less involved in conventional activities.  

A number of studies have attempted to look at the long-term outcomes for children with ADHD. Although there is some variability in the results, it appears that ADHD symptoms remain problematic in two thirds to three quarters of these children in early and middle adolescence, with relative academic and social deficits noted. Antisocial behaviors (and in more severe cases: conduct disorder) may be observed in adolescents with persistent ADHD, and many of these same difficulties persist into late adolescence. 

Adolescents with persisting ADHD tend to exhibit lower grades, fail more courses, have worse performance on standardized tests, have fewer friends, and are rated less adequate in psychosocial adjustment. About 40% continue to experience ADHD symptoms to a clinically significant degree, and 25% - 33% of these adolescents have a diagnosed antisocial disorder. This subgroup - ADHD + antisocial disorder - experiences significant problems, and up to 2/3 of them are arrested. 

The estimates of the percent of children with ADHD who continue to have problems in adulthood vary widely, but anywhere between 1/3 and 2/3 of the children are likely to continue to have problems in adulthood. 

By their mid-twenties, when compared to non-ADHD peers, those with ADHD have completed less schooling, tend to hold lower-ranking occupations, and continue to suffer from poor self-esteem and social skills deficits. In addition, they are more likely to exhibit an antisocial personality and (perhaps) a substance use disorder in adulthood. For example, Fischer, Barkley, et al. (2002) compared young adults who had been diagnosed with ADHD as children to community controls (CC). They found that the ADHD group had significantly higher rates of non-drug psychiatric disorders, were more likely to have ADHD as young adults than the CC group, and had significantly higher rates of major depressive disorder and personality disorders (histrionic, antisocial, passive-aggressive, and borderline personality disorders). Consistent with findings of other researchers, their data indicated that conduct problems in adolescence contributed significantly to the risk of personality disorders, two of which significantly increased the risk for major depression. 

In the discussion above, general patterns were described without respect to subtype of ADHD. Do different subtypes have different outcomes as adults? Murphy et al. (2002) addressed that question by comparing adults with ADHD-combined type (ADHD-C) to adults with ADHD-inattentive type (ADHD-I) and community controls (CC). Both ADHD groups had completed less formal education than the CC group, were less likely to have graduated from college, and were more likely to have received special educational placement in high school. Both groups also reported more alcohol dependence/abuse, more dysthymia, more cannabis dependence/abuse, and more learning disorders, as well as greater psychological distress. Elsewhere on this site, in the article, "ADHD and Safety," site visitors can also learn about the increased rate of accidents (pedestrian and vehicular) and the increased risk of more serious injuries in both children and adults with ADHD. 

But how did the two ADHD groups fare when compared to each other? For the measures employed, the two groups differed in only a few respects: The ADHD-C were more likely to have oppositional behaviors, interpersonal hostility, paranoia, and some history of attempted suicide. They were also more likely to have been arrested than the ADHD-I group. Their findings suggest that the impulsivity of the Combined subtype predicts a poorer outcome as an adult, particularly if there are also conduct problems in childhood. But a more recent study suggests that those with more severe problems of inattention during childhood may be significantly more likely to report frequent episodes of drunkenness, higher alcohol problem scores, and a greater likelihood of substance abuse as teenagers and that impulsivity-hyperactivity was not associated with teenage substance abuse. 

The research described above does not tell the whole story of the ADHD child's adult outcomes, however, and the total picture is not as grim as you might think. Mannuzza and Klein (2000) reported that nearly all of the children followed into adulthood were gainfully employed, and some had achieved a higher-level education (such as a Master's degree or enrollment in medical school) and occupation (e.g., accountant, stock broker). For the studies they reviewed, the authors found that a full two thirds of the children showed no evidence of any mental disorder in adulthood (but as noted earlier, some studies estimate that up to two thirds of children with ADHD will continue to have problems in adulthood). They conclude that although ADHD children, as a group, fare poorly when compared with their non-ADHD peers, ADHD does not preclude attaining high educational and vocational goals, and that most children no longer exhibit clinically significant emotional or behavioral problems once they reach their mid-twenties.

NOTE

[fn 1] The diagnostic criteria are not on this site because of copyright issues, but clicking on the link will take you to a site where they are published.

Information Section: Conditions
Condition: ADHD
Article: Attention Deficit Hyperactivity Disorder Overview
Source: Leslie E. Packer, PhD
File Last Revised: January 20, 2005

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