The initial aim of this study was to replicate the finding of a positive link between hyperactivity-inattention symptoms in childhood and subsequent academic underachievement in young adulthood. We sought to replicate and extend this finding to a large French population-based sample by using a longitudinal design and limiting the spurious logical bias of circularity. Our results corroborate previous research findings showing a significant relationship between ADHD and poor academic achievement (Loe & Feldman). We found evidence of a positive and sizable association between childhood and adolescent hyperactivity-inattention symptoms and negative academic outcomes eight years later. Children with high levels of hyperactivity-inattention symptoms were over two to three times more likely than those with low levels of symptoms to display negative academic outcomes. This was a robust and consistent pattern of association throughout a large series of measures of underachievement (i.e. grade retention, failure in secondary graduation exam, lower diploma achievement, and lower performances in academic subjects). Interestingly, this association was independent from other predictors (particularly conduct disorder symptoms and low socio-economic status) but also remained present after considering school difficulties prior to baseline. This is a methodological strength of our study since it affords inference of causal precedence of risk factors on academic outcomes.
Conduct disorder symptoms accounted for the risk of poor academic achievement in bivariate analysis and after controlling for other risk factors. Our data provide evidence for a link between CD and academic underachievement beyond ADHD. CD core symptoms such as serious violations of rules could lead to school failure through non compliance to basic social and academic rules, truancy from school, and repeated exclusions. Other potential causal mechanisms between CD and poor academic performance could be found in the correlates of CD such as a subaverage verbal intelligence, substance use disorders, and environmental risk factors (Moffit & Lynam, 1994
; Armstrong & Costello, 2002
). Our finding of a link between CD and academic underachievement is consistent with some previous studies (Hinshaw, 1992
) but discrepant with other research reports suggesting that after adjustment for ADHD, CD is no longer a predictor of poor academic outcomes (Fergusson & Horwood, 1995
, Rapport et al. 1999
). The latter surveys argued that CD is unrelated to academic underachievement except through its correlation with ADHD. Our results do not support this view. In his review, Hinshaw (1992)
suggested that only adolescent and not childhood antisocial behaviour and delinquency could be related to academic failure. A possible explanation for the discrepant results could lie in the age range considered, since our sample was older than negative studies samples. Finally, both externalizing disorders independently contributed to heighten the risk of academic underachievement. This finding should be examined in the French context of the study since a controversy remains in France regarding the validity of these two disorders.
Hypotheses on causal mechanisms for the association between ADHD and academic underachievement have already been proposed. It has been posited that ADHD could be related to subsequent poor scholastic achievement through a dual pathway involving behavioural and cognitive mechanisms (Barry et al. 2002
; Mash & Barkley, 2003
; Raggi & Chronis, 2006
; Rapport et al. 1999
). First, and most importantly, ADHD core symptoms of poor concentration, inattention, high distractibility, hyperactivity, impulsivity and motivational deficits appear to play a substantial and direct role in the development of school and academic underachievement. The behavioural core symptoms of ADHD might lead to classroom difficulties through failure to listen to instructions, inability to remember to complete school work, frequent shifting around, excessive verbal and motor activity, and failure to inhibit responses. Interestingly, the negative impact of ADHD core symptoms on academic functioning seems to be independent of executive functioning deficits. Second, the cognitive pathway might involve executive functioning deficits such as inabilities in delay response, working memory, and self-regulation of behaviours. These mechanisms could contribute to our findings, but we could not test them in our data.
It should be underlined that anxious/depressed symptoms and oppositional defiant disorder symptoms did not confer a higher risk for negative academic outcomes in the adjusted models. Considering anxious/depressed symptoms, this result is consistent with previous research showing that a link between early depression and later educational underachievement reflected the effect of confounding factors (Fergusson & Woodward, 2002
). Regarding oppositional defiant disorder little is known about its link with academic achievement, although the bivariate relationship may be overlooked by the association with conduct disorder symptoms.
Parental psychopathology was not a predictor of subsequent academic failure. This might be due to the weakness of our construct of parental psychopathology. It may also correspond to a real absence of association. Indeed a recent survey suggested that adult children of depressed parents do not present a higher risk of low academic attainment (Timko et al. 2008
The study has some methodological limitations. First, attrition was high in this longitudinal data set. However, comparisons between eligible youths and study sample youths in 1991, and comparisons between participants and non-participants in 1999, did not reveal significant baseline differences between participants and non-participants, which lowers the possibility of systematic bias. Hence, our finding of an association between symptoms of hyperactivity/inattention and poor academic outcomes is likely to apply to other community-based populations. Second, participants were recruited among employees of a large state-owned company, which led to the under-representation of individuals with a low socio-economic status in our sample. Since families with a higher socio-economic status were more likely to participate at follow-up, our study represents a rather privileged population. As a result, in other, more varied populations, associations between symptoms of hyperactivity/inattention and academic achievement may be stronger than we report. Third, a measurement bias might have arisen from the use of self-reported questionnaires. However, self-reporting is known to involve less desirability bias than face-to-face questionnaires (Tourangeau & Yan, 2007
), implying that such bias is likely to be negligible. Fourth, we used CBCL scores to obtain proxy DSM diagnoses. Consequently we had no formal diagnosis of ADHD since symptom duration and associated impaired functioning could not be considered through the empirically-based and DSM-oriented scales. However, DSM-oriented scales have shown high levels of validity in terms of significant associations with DSM clinical diagnoses (Achenbach et al 2003
). Particularly for CD and ODD, DSM-oriented scales have shown a good level of predictive power of DSM-IV diagnoses (Krol et al. 2006
) showing respectively for CD/ODD problems the following figures: positive predictive power (0.80/0.58), negative predictive power (0.97/0.64), sensitivity (0.88/0.55), specificity (0.86/0.86), coefficient phi (0.64/0.42). In addition, this measure of hyperactive-inattention symptomatology allowed us to avoid, at least partially, a circularity bias (by dropping the item “poor school work”), which was a strength of our study. Nevertheless, it must be acknowledged that our study, as any study that investigates the association between ADHD and school performance, is subject to residual circularity. Indeed, the clinical definition of ADHD symptoms includes concentration problems, which are typically appreciated in school situations and often reported by teachers to parents. Hence, a reported concentration problem might directly reflect poor school performance. However, poor concentration is per se an important causal precedence of risk factor on academic outcomes, especially since hyperactivity-inattention symptoms are generally present in preschool years. Thus it cannot be entirely excluded that GAZEL Youth study participants with high levels of symptoms of hyperactivity/inattention had some school-related difficulties prior to baseline. Fifth, we could not consider ADHD subtypes (i.e. inattentive, hyperactive/impulsive or combined), which precludes our ability to explore symptom profiles specifically related to academic outcomes. Sixth, there was a slightly higher female ratio in the follow-up participants. Since females are known to exhibit more often the inattentive ADHD subtype, this could have introduced a potential bias. However, we controlled for gender in the statistical analyses. Finally, we controlled for environmental risk factors (i.e. SES, parental psychopathology, and parental marital status) and child comorbid psychopathology (i.e. conduct disorder symptoms, oppositional defiant disorder symptoms, and anxious/depressed symptoms). However, other factors such as IQ levels, learning disability, executive functioning deficits, bipolar disorder status, adult ADHD status, treatment status, and genetic or biological factors, which might also play a confounding role, were not considered in the present study. Such factors should be controlled for in future studies.
Caution is required regarding the external validity of the results, especially because our sample was potentially biased towards healthier subjects. Nevertheless, owing to the consistent repeated positive link between hyperactivity-inattention symptoms and academic underachievement, and given the importance of the adverse outcomes related to low academic attainment, children with hyperactive-inattention symptoms should be identified and constitute a target for early interventions. Interestingly, stimulant medication has shown a significant effect on classroom measures of attention, cognitive tasks and academic efficiency (Carlson et al. 1991
; DuPaul & Rapport, 1993
; Elia et al. 1993
). With regard to studies of long-term treatment of ADHD by stimulant medication, recent papers suggested a significant reduction in ADHD core symptomatology and a small effect size of stimulants on academic outcomes (Barbaresi et al. 2007
, Schachar et al. 2002
; Van der Oord et al. 2008
). In addition, there is little research in ADHD children with respect to the effect of non-pharmacological interventions (such as school support programs, cognitive-behavioural therapy, or supportive therapy) or combined interventions (medication plus psychosocial treatment) on academic outcomes. However, preliminary findings suggest some value of academic interventions such as peer tutoring, computer-assisted instruction, task/instructional modifications, self-monitoring, strategy training, or homework-focused interventions (Raggi & Chronis, 2006
). Further research is required to determine what type of intervention would benefit ADHD children at risk of academic failure.
Childhood hyperactivity-inattention symptoms are associated with academic underachievement in young adulthood. This finding may lead to better detection of ADHD and academic difficulties at school, so that adequate school support may be given and that children may be referred to health professionals. It may guide clinicians in detecting and managing interventions in children and adolescents with ADHD, especially when academic difficulties and conduct problems are present.