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How Often Does ADHD Persist into Adulthood?
How often does ADHD persist into adulthood? This is an important question, but a difficult one to answer because it requires following a group of ADHD children for many years to determine whether they still qualify for the diagnosis as adults. Tracking children over many years can be an enormous challenge, and, to date, there have been only three published studies in which at least 50% of the original sample has been followed from childhood into young adulthood.
Results regarding the persistence of ADHD based on the results of these studies have been mixed. In one study that began with 104 children, about two-thirds reported they were still troubled as adults (i.e. average age at last follow-up of 25) by at least one or more disabling core symptoms of the disorder, and one-third reported at least moderate-to-severe levels of hyperactive, impulsive, and inattentive symptoms.
In a second study conducted in Sweden, 49% of participants diagnosed with ADHD as children reported marked ADHD symptoms at age 22, compared to only 9% of control participants. Although results from these studies indicate that many ADHD children continue to struggle with core ADHD symptoms as adults, formal diagnostic criteria were not used in either study. Thus, it is not possible to determine the percentage of participants who continued to qualify for an ADHD diagnosis as young adults.
In the only longitudinal study in which DSM (Diagnostic and Statistical Manual of Mental Disorders) diagnostic criteria were employed (Manuzza et al., 1998), it was reported that only 8% met full diagnostic criteria at age 26. (Note: A prior version of the DSM criteria from DSM-III was used in this study because that was the standard at the time. You can review current diagnostic criteria here.)
These results imply that the vast majority of children with ADHD outgrow the diagnosis by early adulthood, and have led some to speculate that the adverse impact of ADHD becomes increasingly benign with advancing age.
Is it really the case that less than 10% of children diagnosed with ADHD will continue to meet diagnostic criteria in adulthood? Recently, Dr. Russell Barkely -- widely recognized as a leading authority on ADHD -- has identified two factors that may have contributed to this result. First, Barkely notes that, although participants were diagnosed as children based largely on reports about their behavior provided by others (i.e. parents and teachers), their diagnostic status as adults was determined exclusively by their own reports. Barkely suggests that that this switch could account for the low rates of adult ADHD reported, particularly since adults with ADHD may not provide accurate appraisals of their own behavior.
A second problem noted by Barkely is that, although the manifestations of ADHD may change over time, current diagnostic criteria are the same for adults as they are for children. Thus, the same symptoms are used to diagnose children and adults and the same number of symptoms is required. This could artificially reduce the likelihood that an individual would be diagnosed with ADHD in adulthood for two reasons. First, if the manifestations of ADHD change over time, then the symptoms used to define the disorder in childhood may not include features that are more characteristic for adults.
Second, if ADHD symptoms as currently defined decline with age -- as they are known to do -- then it becomes increasingly unlikely for individuals to display the required number of symptoms as they become older. As a result, Barkely suggests that the number of symptoms necessary for the diagnosis should vary with age. For example, suppose an individual displayed eight hyperactive symptoms at age seven and only four of these symptoms at age 25. This individual would no longer qualify for an ADHD diagnosis based on current standards even though he might be just as "deviant" relative to same-age peers at age 25 as he was at age seven. If this were the case, Barkely argues that the individual will appear to have "outgrown" the disorder by adulthood, "...whereas in fact they have only outgrown the criteria."
To account for this, Barkely suggests using age-adjusted criteria for the number of symptoms required rather than the fixed threshold method currently used. Specifically, he argues that the number of symptoms required should be that which occurs in less than 2.5% of the population of individuals that age. This number would be lower for adults than for children, but adults showing this reduced number of symptoms would still be as deviant relative to their same-age peers as are children displaying a greater number of symptoms.
How frequently does ADHD persist from childhood into adulthood when these two factors identified by Barkely are taken into account? This issue was examined in a study published recently in the Journal of Abnormal Psychology (Barkely, R.A. et al (2002). The persistence of AD/HD into young adulthood as a function of reporting source and definition of disorder, 111, 279-289).
Participants in this study were 158 young adults (ages 19-25) diagnosed with ADHD at an ADHD specialty clinic when they were between 4 and 12 -years old. Eighty-one comparison subjects without ADHD from the same community were also followed into young adulthood. Over 90% of individuals in both groups participated in the young adult evaluation, an extremely high retention rate for a study in which individuals were followed over so many years.
To determine ADHD status in young adulthood, two different methods were used. First, participants' own reports of ADHD symptoms and ratings of their functioning in important life areas (e.g. school, work, peer relationships) were used to determine whether they met diagnostic criteria. Determining diagnostic status based on the self-reports of young adults is the method that had been used in the study referenced above.
Second, parents of these young adults were asked to provide ratings of their child's ADHD symptoms so diagnostic status based on parent ratings could be determined. Parent reports of their child's behavior were the basis on which the diagnosis had originally been made, and Barkely hypothesized that the continuity of ADHD from childhood to young adulthood would be much greater when parents were used to provide information on their child's behavior as an adult than when participants self-reports were the sole source of data.
Results
How did self and parent ratings of current ADHD symptoms compare?
Young adults in the childhood ADHD group did not differ from control subjects in the number of ADHD symptoms they reported, with group averages of 2.1 and 1.5, respectively. (Note - This is out of a total of 14 possible symptoms from DSM-III-R, which was the diagnostic system in place when the data were collected. Currently, DSM-IV lists 18 specific symptoms of ADHD.) In contrast, parents reported an average of 9.2 symptoms for adults in the childhood ADHD group vs. 1.7 for comparison subjects.
Based on self-report data, only 5% of young adults diagnosed with ADHD as children met current diagnostic criteria for ADHD. When parent reports were used, however, 58% of these young adults met full diagnostic criteria for ADHD. And, when the number of symptoms required for the diagnosis was adjusted to reflect the fact that ADHD symptoms tend to diminish with increasing age (see discussion above), this figure increased to 66%.
How valid are self and parent reports of ADHD symptoms in adulthood?
As indicated above, among young adults with childhood ADHD, self and parent reports of current ADHD symptoms differed dramatically. Which reports were likely to be more accurate?
One way to examine this is to determine whether self or parent reports were more strongly related to how well the young adults were doing in various important life activities. The life areas considered were: years of education, high school GPA, class rank during the last year of high school, employer-rated ADHD symptoms, employer-rated work performance, and number of arrests. When the authors looked at how well parent and self-reports of ADHD symptoms predicted these life outcomes, they found that parent reports were superior in every case. This provides compelling evidence that parent reports had greater validity than reports from the adults themselves. The only outcomes predicted by self-reported ADHD symptoms were the number of ADHD symptoms reported by the employer and employer-rated work performance. Even in these areas, however, parent reports were the stronger predictor.
The authors also examined how young adults in the childhood ADHD group were faring in these areas compared to adults in the comparison group. In every area, they were found to be struggling: they had fewer years of education (12 years vs. 13.6 years), a lower high school GPA (1.7 vs. 2.5) and class rank (29th percentile vs. 49th percentile), were rated as showing more ADHD symptoms by their employer, had lower employer job ratings (3.2 vs. 4.2 on a 1-to-5 scale), and a greater number of arrests (.8 vs. .2). (Note: All figures reported are group averages). Interestingly, these adults were also significantly more likely to be living at home.
Summary And Implications
Results from this study make it clear that estimates of the persistence of ADHD into young adults varies dramatically depending on whether parents or young adults themselves are the source of information used to make diagnostic decisions. When the information used is restricted to adults' self-reports of ADHD symptoms, it will seem as if the persistence of ADHD is very infrequent. However, when parental reports are used, the persistence of ADHD becomes a far more frequent occurrence.
This was especially true when the diagnostic threshold for ADHD in adulthood was adjusted to reflect the fact that ADHD symptoms tend to diminish with age. When this adjustment was made, two-thirds of individuals with ADHD continued to meet diagnostic criteria as young adults. It should be noted that Barkely's suggestion to adjust the diagnostic criteria based on age is not something that everyone agrees with and is not the current standard in the field. Whether this suggestion will be incorporated into the next round of diagnostic criteria for ADHD remains to be seen.
Results from this study also suggest that parent ratings of their adult children's ADHD symptoms are likely to be more accurate than young adults' ratings of their own symptoms. Across multiple measures of educational and occupational functioning, parental reports of ADHD symptoms were better predictors of outcome than reports from the young adults. The authors speculate that this may be the case because the diminished frontal lobe activity that is found in many individuals with ADHD may be associated with less accurate self-appraisal among ADHD adults.
It is tempting to interpret these results as indicating that adults with ADHD are typically inaccurate sources of information about their own functioning, and that it is problematic to rely on adults' self reports for making diagnostic decisions. Although this conclusion appears to follow directly from the study's results, it is difficult to reconcile with the fact that many adults with ADHD are acutely aware of their struggles and seek out evaluation and treatment for that reason. What could account for this apparent discrepancy? Two possibilities come to mind.
First, it is important to remember that adults in this study were not seeking treatment, but were being evaluated as part of an ongoing research project. It seems reasonable to hypothesize that adults who seek treatment for ADHD are quite different from those who do not, and that the former may be better able to report accurately on their symptoms and behaviors related to ADHD. Thus, one should not interpret the results of this study to indicate that adults' reports of ADHD symptoms will invariably underestimate what is actually the case.
A second possibility has to do with the manner in which information about ADHD symptoms was obtained in this study. Adults were simply asked to rate how often ADHD symptoms occurred, on a 1-to-5 scale ranging from "not at all" to "almost always". Symptoms rated as occurring "frequently" -- this was the midpoint on the scale -- were counted as "present". It thus appears that only a single question pertaining to each symptom was used to classify it as "present" or "absent". This may have resulted in fewer symptoms being counted as "present" than if the researchers had conducted a more extensive interview and done more in-depth probing of the different symptoms of ADHD. Thus, the method used may not have been as sensitive as it needed to be.
In spite of these two possibilities, results from this study certainly support the value of obtaining information about ADHD symptoms from multiple sources when evaluating an adult for ADHD. This is certainly the procedure recommended when evaluating children, and this study highlights the value of this approach in adult evaluations as well.
It is also important to emphasize that, regardless of whether the adults in this study continued to meet full ADHD diagnostic criteria, those in the childhood ADHD group were clearly having difficulty relative to other adults. These findings highlight the long-term adverse effects that ADHD can have on individuals' development, and the compelling need that many individuals have for ongoing support and treatment, even when they may no longer meet full diagnostic criteria.
Note: This article originally appeared in Attention Research Update, an online newsletter written by Dr. David Rabiner, a Duke University psychologist and former member of CHADD's Professional Advisory Board. You can learn more about Attention Research Update and sign up for a free subscription at www.helpforadd.com.