Does Childhood Executive Function Predict Adolescent Functional Outcomes in Girls with ADHD?

Our chief aim was to determine whether, in girls with and without ADHD, childhood levels of EF could predict adolescent functional outcomes across the domains of academic achievement, social functioning, and global functioning. By using well-established measures of EF as well as several well-validated criterion measures in domains of central importance to healthy functioning, we found that, under tight statistical control, childhood EF predicted adolescent outcomes in academic achievement (including WIAT Math scores and a dichotomous measure of PA in academic achievement) and social functioning (both teacher-appraised peer status and a dichotomous measure of PA in social skills) across the entire sample. Although group status did not emerge as a statistically significant moderator of any associations, separate examination of predictive associations in the ADHD and comparison groups revealed that childhood EF predicted adolescent global functioning in girls with ADHD but not in comparison girls, independent of IQ. In all cases of significant associations, better EF scores at baseline predicted better adolescent outcomes.

In terms of academic achievement, childhood EF as measured by the ROCF EPS and CPT omissions predicted academic achievement outcomes in adolescence across our whole sample (WIAT Math scores, academic achievement PA), with group status controlled. These findings are in line with research showing that children with ADHD and EF deficits have lower academic achievement than those without EF deficits or than non-ADHD comparison youth (Biederman et al. 2004). However, because these predictive associations were significant in our whole sample (with group status failing to moderate this association), our findings indicate that poorer EF scores predict lower academic achievement (namely math achievement) in all girls. This finding is important because it suggests that intervening with EFs may be one possible way to preclude academic difficulties not just in children with specific psychiatric diagnoses, like ADHD, but in typically developing children as well.

None of our baseline EF measures uniquely predicted WIAT Reading scores. One reason for this negative finding could be that word reading (the skill tapped by the WIAT Basic Reading composite score) becomes automatic for most youth during elementary school (Chall 1983), whereas math skills are cumulatively learned over time, throughout middle and high school. The association between baseline ROCF EPS and follow-up WIAT Math scores could also be explained by the strong visuospatial nature of both of these measures.

In terms of social functioning across our entire sample, childhood EF as measured by CPT omissions and CPT commissions predicted teacher-rated social preference in adolescence across our whole sample when controlling for group status. Additionally, the ROCF EPS joined the CPT indicators in predicting peer acceptance PA across the whole sample. These whole-sample predictions suggest the importance of the abilities to both inhibit one’s behavior (i.e., be less impulsive) and pay attention to relationships and social interactions with respect to peer regard. These results are in contrast to other studies finding no such linkages (e.g., Biederman et al. 2004) but are consistent with research showing that EF impairment has a negative impact on peer acceptance in girls with ADHD (Diamantopoulou et al. 2007) and on social relationships in individuals with autism spectrum disorders (Gilotty et al. 2002). Diamantopoulou et al. ( 2007) also found that the association between EF deficits and peer acceptance was more pronounced in girls with ADHD than in boys with ADHD (who exhibited equivalent symptomatology), which may be related to (a) the gender-atypical nature of ADHD symptoms in girls and/or (b) girls’ penchant for engagement in relational aggression (Zalecki and Hinshaw 2004). Overall, our findings within the realm of social functioning indicate that interventions targeting EF could potentially prevent social difficulties in girls, particularly those with ADHD, who are at high risk for having social problems (e.g. Hinshaw and Blachman 2005).

For global functioning across the whole sample, childhood EF did not predict the global functioning measure (CIS) in adolescence. However, because the correlation between childhood ROCF EPS and adolescent CIS was statistically significant, we explored this association further via separate regression analyses in each group (ADHD vs. comparison). These analyses showed that childhood ROCF EPS predicted adolescent CIS when controlling for IQ in the ADHD group, but not in the comparison group. Although previous studies have not found associations between EF deficits and global functioning in those with ADHD (Biederman et al. 2004), our findings are corroborated by research into the role of EFs in functional impairments in non-ADHD populations (e.g., Alzheimer’s disease), which reveal that executive dysfunction can explain a large proportion of the variance in activities of daily living, a global measure of functional abilities (Boyle et al. 2003). Additionally, a recent study found that EFs moderated the association between temperament and global functioning in a sample of typically developing preschoolers (Healy et al., in press). Although such associations were not explored in the present study, combining these findings with ours suggests the importance of intact EFs in terms of global outcomes. In all, this finding amplifies our earlier domain-specific results with respect to academic and social functioning, suggesting strongly that deficits in EF in childhood have a wide-ranging impact on later functioning for girls with ADHD. These findings also reemphasize the potential importance of treatments that target EFs in order to prevent the development of difficulties across many life domains.

It is of interest that the EPS method of scoring the ROCF was a stronger predictor of functional outcomes than was the more traditionally used organization score. This pattern of results may seem counterintuitive, as the organization score taps overall perceptual conformation and has been shown to be developmentally sensitive (Bernstein and Waber 1996). Yet our own previous work has shown that the EPS method was able to distinguish between girls with ADHD and comparison girls whereas the organization method was not (Sami et al. 2003). Combining these findings with the results from the present study suggests that the EPS is better at differentiating girls with ADHD from comparison girls than the Developmental Scoring System’s organization score and may be more useful in terms of predicting adolescent outcomes. It may be that the EPS method of scoring the ROCF allows for the measurement of a large number of EFs within one scoring system (e.g., planning, working memory, inhibitory control, organization, reasoning). Therefore, the EPS may be better able to tap the complex nature of the ROCF as a global EF measure by assessing multiple aspects of EF at once.

It is also of interest that the CUL did not predict of any of the functional domains assessed. The reason for the CUL’s poor predictive power is unclear. It is possible that this task requires less effortful control than initially thought, and may be too simple to require extensive EF. It could also be that it requires more visuospatial abilities than executive abilities, although given that the ROCF has a strong visuospatial component, this would seem a less likely possibility.

Our findings highlight the non-specificity of EF deficits, given that most of the associations between baseline EF measures and follow-up functional measures were found across the entire sample and not solely in the ADHD group. Although other studies have not found that EF deficits affect functional outcomes in control participants (Biederman et al. 2004), our findings are in line with work by Bull et al. ( 2008), who found an association between EF and learning in general in a longitudinal study of non-clinical preschoolers. As described earlier, EFs include such abilities as planning, organizing tasks and behavior, attentional and inhibitory control, reasoning, and working memory (Pennington and Ozonoff 1996; Tranel et al. 1994). If such aspects of EF are impaired during childhood, it seems likely that academics and social abilities would be significantly and cumulatively influenced over time, regardless of one’s psychiatric diagnosis (or lack thereof). For example, imagine a child who has difficulty organizing her schoolwork, keeping the teacher’s instructions or a conversation with a friend in working memory, and reasoning. Without intervention to improve such deficits, a pattern of performance would be likely to develop resulting in concurrent and future problems in other domains relying on EF abilities. She may lose assignments, miss instructions, and have poor relations with her peers, resulting in lower grades and fewer positive social interactions. Given our findings, it seems likely that this detrimental effect of EF deficits on later performance is present in all girls exhibiting EF difficulties, regardless of psychiatric diagnosis.

Limitations include the fact that the baseline neuropsychological battery was formulated approximately 15 years ago; including other newly developed measures of EF may well have been useful. Additionally, the degree to which these predictive associations would appear in a representative community sample of girls with ADHD is not clear, as our sample was derived clinically, ascertained from medical, mental health, and school sources as well as advertisements (see Hinshaw 2002). Although there are other outcome domains of importance, such as substance use, this outcome will become more sensitive as our sample ages into young adulthood. It is also possible that the restricted range in the comparison sample contributed to our finding of significant EF-global functioning associations in the ADHD group but not in the comparison group. Additionally, although the associations we found were statistically significant and robust to statistical control of key covariates, there are multiple other factors that contribute to adolescent outcomes aside from EF. Certainly genetic, psychosocial, family, and other environmental factors play significant roles. Indeed, it is likely a complex interaction among these variables—including neuropsychological variables—that is the best predictor of adolescent outcomes. This is an important question for future research. Finally, because our sample is entirely female, generalizability to boys cannot be assumed.

Overall, our findings are consistent with research that has shown that EF deficits predict academic difficulties (Biederman et al. 2004) and that EFs are involved in social abilities (Diamantopoulou et al. 2007), potentially serving as precursors to successful social interactions by bolstering certain underlying constructs such as ToM (Hughes and Ensor 2007; McEvoy et al. 1992). Because approximately half of individuals with ADHD display distinct EF deficits (Nigg et al. 2005), understanding the potential consequences of these deficits is important, particularly because they appear to persist through adolescence (Hinshaw et al. 2007). Additionally, because our findings suggest that EF predicts various outcome domains across our entire sample (including comparison girls), it seems important to evaluate EF deficits in seemingly typically developing children in addition to those at high-risk for EF deficits. These results again emphasize the non-specificity of EF deficits and their effects.

Our findings may help to consider preventive interventions across other samples displaying EF impairments, such as children with autism or those from low socioeconomic backgrounds (see Kishiyama et al. 2009). Relevant interventions may include computerized EF training and organizational skills training. Indeed, interventions that specifically target improving EFs in preschool children have shown promising results (Diamond et al. 2007). This intervention is particularly interesting given its integration into classroom settings. Other computerized interventions focusing on specific aspects of EF (namely, working memory) have also been shown to be effective in reducing symptom severity and improving working memory in children with ADHD (Klingberg et al. 2002; Klingberg et al. 2005); one study showed increases in prefrontal and parietal activity during working memory tasks after treatment (Olesen et al. 2003). Although this working memory training paradigm is indeed promising, it will be important for researchers other than the developer to replicate such results. Also, our results provide initial support for screening children for EF deficits to initiate preventive measures, although far more work on psychometrics and predictive validity is needed before such an endeavor can become a reality. Additional longitudinal work investigating the predictive associations between early EF deficits and functional outcomes across a variety of populations displaying significant EF difficulties is of high priority, as are data regarding the effectiveness of EF training programs for children with distinct EF deficits.