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How Does Young Adult Outcome Relate to Childhood ADHD, Aggression, and Stimulant Medication Use?
This important question was examined by researchers addressed in a study published recently in the Journal of Child and Adolescent Psycho- pharmacology (Paternite, Loney, Salisbury & Whaley, 1999, Childhood Inattention-overactivity, aggression, and stimulant medication history as predictors of young adult outcome. JCAP, 9 , 169-184). This is one of the few studies yet conducted in which the long-term effects of stimulant medication treatment have been examined and is thus an important addition to thetreatment literature on ADHD.
These authors were interested in determining how ADHD symptoms, aggression, and a child's history of stimulant medication treatment related to outcome in young adulthood. This type of longitudinal work - i.e. following a group of children identified with ADHD over time - is critically important for understanding the long-term impact of ADHD and how medication treatment may effect children's outcomes. This latter question is especially important because although many studies have documented the short-term benefits of medication, and more recent work has indicated that such benefits persist beyond a year (see the MTA study as an example of this), there is virtually no research to indicate that medication treatment during childhood results in meaningful improvements in young adult functioning.
Participants in this study were 121 boys who were initially diagnosed with ADHD when they were between 4 and 12 years old. These boys were diagnosed back in the 1970s, and the diagnostic criteria in use at that time were substantially different then they are today. In fact, in the official terminology in use at that time the boys were diagnosed with either hyperkinetic reaction of childhood (HK) or minimal brain dysfunction (MBD). Using detailed information about specific symptoms contained in boys' medical charts, however, the authors estimated that approximately 71% of these boys would have qualified for a diagnosis of ADHD using today's diagnostic criteria.
All 121 boys were treated with stimulant medication (i.e. methylphenidate) and their treatment with medication was initiated between 1967 and 1972. (It would have been preferable, of course, if girls were also included in this sample. Several decades ago, however, females were probably even less likely to be recognized as having ADHD than they are today, so it is not surprising that only boys were available to follow.)
Based on information contained in these boys, medical records, the authors created scores for each boy that provided an indication of the strength of both ADHD symptoms (i.e. inattention and hyperactivity/impulsivity) and aggression. These ratings were made based on information from parents, teachers, and the boys themselves that were included in the boys' charts. Because prior research has clearly shown that ADHD symptoms and aggression both make independent contributions to children's long-term development, these two aspects of children's behavior were considered separately. (The authors actually hypothesized that childhood aggression would be more strongly associated with negative outcomes in young adulthood than would ADHD symptoms.)
As noted above, all participants in this study were treated with stimulant medication at some point. Thus, the authors were not comparing the long-term outcomes of children with ADHD according to whether or not they had received medication. Instead, they carefully reviewed boys' medical records to document the characteristics of the medication treatment that was provided. They then examined how important aspects of medication treatment - i.e. overall response to medication, dose of medication received, and duration of medication treatment - were related to various outcomes in young adulthood. These ratings were based on information contained in the boys' charts and were made by raters who were blind to how the boys were doing in young adulthood.
The young adult assessment occurred when participants were between 21 and 23 years old. Approximately 80% of the original sample participated in the young adult evaluation, and those who did were representative of the sample as a whole. A wide variety of measures were collected at this assessment including information on psychiatric diagnoses, overall level of functioning in important life areas, intellectual functioning, academic achievement, and overall life circumstances (i.e. social, educational, and employment circumstances). Within each of these broad domains, a number of different measures were included so the overall number of outcome measures considered was quite large. This assessment thus provided a comprehensive account of how participants were faring at this point in their lives.
Results
The basic questions of interest in this study are as follows:
- 1. How do childhood levels of ADHD symptoms relate to functioning in young adulthood?
- 2. How does childhood level of aggressive behavior relate to functioning in young adulthood?
- 3. Does young adult outcome relate to a child's overall response to stimulant medication, the magnitude of the dose a child typically received, and/or the duration of medication treatment?
This last question is actually quite important as there are distressingly few long-term studies of the effect of stimulant medication treatment on important outcomes for children with ADHD. As noted above, the authors of this study were not comparing outcomes for children with ADHD depending on whether they were treated with medication. Instead, they were interested in how important aspects of medication treatment (i.e. overall response, dose, and duration) predicts important life outcomes over a a number of years.
Because of the large number of outcome measures collected, it is perhaps more important to look at the overall pattern of results rather than focusing on specific outcome variables. When the results of the study are considered in this way, they are really quite clear.
Overall, childhood aggression was a stronger predictor of problems in young adulthood than was childhood ADHD.
The authors reported that aggression was uniquely related to 38% of the outcomes they considered while ADHD symptoms predicted only 10% of these outcomes. Among the specific outcomes predicted by childhood aggression were depression, drug abuse, antisocial personality disorder, and a variety of functional impairments. ADHD symptoms, in contrast, predicted only lower levels of employment and greater general levels of impairment.
Thus, these results clearly indicate that high levels of aggression during childhood poses significantly greater risks to a child's long-term development than do ADHD symptoms alone.
Children who had a better overall response to medication, who received higher doses, and who were treated for a longer duration, had better outcomes in a variety of different areas.
The aspects of medication treatment the authors examined - i.e. overall response, dose, and treatment duration - were not related to all of the different outcomes considered. For 11 different outcome measures, however, these aspects of medication treatment were found to be significant predictors, and in every case but one, results were in the direction of indicating significant benefits for medication.
Thus, it is reported that better overall response to medication was associated with lower depression scores and better social functioning in young adulthood. They were more likely to be living independently of their parents, and to be either married or engaged. Similarly, children treated with higher doses were less likely to be diagnosed with alcoholism in young adulthood and had made significantly fewer suicide attempts. Finally, the longer a child was treated with medication the higher his IQ and academic achievement in reading and math was likely to be. The only clear negative finding was that children who had a better overall response to medication treatment were less likely to graduate from high school. This is a perplexing finding given the overall pattern of results, and may represent a chance finding that would not be replicated. In general, however, medication treatment tended to have positive effects long after it had been discontinued.
Implications And Limitations
What seems fairly clear from these results is that childhood aggression as measured in this study is associated with poorer young adult outcomes. Also, MPH treatment is associated with better young adult outcomes. Specifically, positive outcomes occur in psychiatric, cognitive, academic, and social domains when considered in children who respond well to early treatment and who were treated with higher doses for a greater period of time.
These results, although informative and potentially influential, should be viewed with caution in regards to what can be concluded about the long-term benefits of stimulant medication treatment. There are several different reasons why such caution is necessary. First, no information is provided about the families of these patients or the total number of clinical visits each child made. It may be that more frequent visits to the doctor - which would be likely to correlate with a greater duration of medication treatment - is indicative of a more concerned family, or a family that is more invested in their child's well-being. Conceivably, the child's improvement could be a consequence of this investment rather resulting from more extensive treatment with medication.
It is also important to keep in mind that the diagnostic criteria for ADHD in use at the time the children in this study were first diagnosed were quite different than they are today. Thus, not every child in this study would be diagnosed with ADHD using current guidelines and the degree to which these data would apply to children diagnosed today is not completely clear. In establishing the long-term effects of medication treatment, it would also be important to compare outcomes for children who did, and did not, receive treatment with medication. That was not done in the current study, although the authors indicate that they have additional papers on using this data set in which such comparisons are described. Finally, there were no girls included in the sample so the extent to which these findings would generalize to girls is completely unknown.
Despite these limitations, the value of this study is clear. The keys points to emphasize is that aggression during childhood appears to be a better predictor of negative long-term outcomes than ADHD symptoms alone. This replicates findings that have been reported in prior work, and underscores the importance of carefully attending to this aspects of children's behavior. When a child has both ADHD and aggressive behavior problems, parents and professionals need to be especially vigilant to make sure that interventions which address the aggressive behavior problems are an important part of the child's treatment.
In regards to medication treatment, these data do provide important initial support that such treatment is associated with long-term benefits. When children have a good response to meds, receive an adequate dose, and are maintained on medication over a longer period of time, they are likely to benefit as a result. This is not conclusive proof by any means that stimulant medication produces meaningful long-term gains, but it is certainly consistent with this hypothesis and is a step in the right direction of establishing such proof. I look forward to future publications from these authors and will include summaries of their work in ADHD RESEARCH UPDATE as it appears.
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.