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.
Over the years, I have occasionally encountered references to a possible connection between ADHD and visual problems that might be related to reading disabilities. Although a search of Medline did not turn up too many articles, I thought I would share a few of the reports with site visitors.
The first question, of course, is whether there is any demonstration that children with ADHD are different from the non-ADHD population in terms of visually related processes. Farrar et al. (2001) compared children who had been diagnosed with ADHD and who were under pharmacological treatment for ADHD to age- and gender-matched controls on parental and self-reports of visual symptoms and quality of life issues. The ADHD reportedly experienced more symptoms of visual system dysfunction than their age-matched control peers: 14 of the 33 symptoms on the survey were found to be significantly more severe in the ADHD group than in the control group. Thus, even with pharmacological treatment, there was some indication that children with ADHD may have more visual (and quality of life) symptoms than non-ADHD children.
But what specific kinds of problems might relate to reading disabilities? Several studies have indicated that children with ADHD have significantly more deficits in saccadic control. They have more difficulty in inhibiting movements and display greater variability. The implications are that children with ADHD who have such visual deficits may have more trouble sustaining their visual attention on targeted stimuli (such as reading material) and in suppressing unwanted visual activity away from the targeted material. Approximately one half of children with dyslexia display abnormalities in saccadic control.
Although a full discussion of this complex research area is beyond the scope of this web site, it is helpful for educators to be aware that some of the visual attention and reading problems observed in a child with ADHD may be linked to an oculomotor disturbance. Thus, 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.
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.