Are changes in ADHD course reflected in differences in IQ and executive functioning from childhood to young adulthood?

Jessica C Agnew-Blais,Louise Arseneault,Andrea Danese,Jasmin Wertz,Guilherme V Polanczyk,Terrie E Moffitt

doi:10.1017/s0033291719003015

Abstract

Attention-deficit hyperactivity disorder (ADHD) is associated with poorer cognitive functioning. We used a developmental, genetically-sensitive approach to examine intelligence quotient (IQ) from early childhood to young adulthood among those with different ADHD courses to investigate whether changes in ADHD were reflected in differences in IQ. We also examined executive functioning in childhood and young adulthood among different ADHD courses. Study participants were part of the Environmental Risk (E-Risk) Longitudinal Twin Study, a population-based birth cohort of 2232 twins. We assessed ADHD in childhood (ages 5, 7, 10 and 12) and young adulthood (age 18). We examined ADHD course as reflected by remission, persistence and late-onset. IQ was evaluated at ages 5, 12 and 18, and executive functioning at ages 5 and 18. ADHD groups showed deficits in IQ across development compared to controls; those with persistent ADHD showed the greatest deficit, followed by remitted and late-onset. ADHD groups did not differ from controls in developmental trajectory of IQ, suggesting changes in ADHD were not reflected in IQ. All ADHD groups performed more poorly on executive functioning tasks at ages 5 and 18; persisters and remitters differed only on an inhibitory control task at age 18. Differences in ADHD course - persistence, remission and late-onset - were not directly reflected in changes in IQ. Instead, having ADHD at any point across development was associated with lower average IQ and poorer executive functioning. Our finding that individuals with persistent ADHD have poorer response inhibition than those who remitted requires replication.

Highlights

Attention-deficit hyperactivity disorder (ADHD) is associated with poorer cognitive functioning
We did not find that changes in the outward manifestation of ADHD – namely the disorder’s remission, persistence and late-onset from early childhood to young adulthood – were reflected in changes in intelligence quotient (IQ) and executive functioning
The associations between ADHD and IQ were stable across development and independent of whether ADHD was evident at a particular developmental stage

Summary

Methods

Participants were members of the E-Risk Longitudinal Twin Study, a birth cohort of 2232 British children drawn from a larger birth register of twins born in England and Wales in 1994–95 (Trouton et al, 2002). The E-Risk sample was constructed in 1999–2000 when 1116 families (93% of those eligible) with the same-sex 5-year-old twins participated in home-visit assessments administered by trained research workers. Childhood ADHD diagnoses were based on DSM-IV criteria: participants had to have six or more symptoms of inattention or six or more symptoms of hyperactivity-impulsivity reported by mothers or teachers in the past 6 months, and the other informant must have endorsed at least two symptoms (thereby meeting the diagnostic criteria for the presence of symptoms in more than one setting). The requirement of symptom onset prior to age 12 was met if parents or teachers reported more than two ADHD symptoms at any childhood assessment. We compared those with remitted, persistent and late-onset ADHD to those who never had ADHD on executive functioning composite score at age 5 and on CANTAB tasks of working memory and response inhibition at age 18 using logistic regressions adjusting for sex and childhood SES.

Results

Discussion

Limitations