Evaluation of the Persistence, Remission, and Emergence of Attention-Deficit/Hyperactivity Disorder in Young Adulthood

Abstract

Importance ADHD is now recognized to occur in adulthood and is associated with a range of negative outcomes. However, less is known about the prospective course of ADHD into adulthood, the risk factors for its persistence past childhood, and the possibility of its emergence in young adulthood in non-clinical populations. Objective To investigate childhood risk factors and young adult functioning of individuals with persistent, remitted and late-onset ADHD. Design, Setting and Participants The study sample is the Environmental Risk (E-Risk) Longitudinal Twin Study, a UK nationally-representative birth cohort of 2,232 twins born in England and Wales in 1994–1995. Main Outcome Measures ADHD diagnoses were assessed in childhood at ages 5, 7, 10, and 12 and in young adulthood at age 18. Childhood predictors included pre/perinatal factors, child clinical characteristics and aspects of the family environment. Age-18 outcomes included ADHD symptoms and associated impairment, overall functioning and other mental health disorders. Results Among individuals with childhood ADHD (n=247), 21.1% met diagnostic criteria for the disorder at age 18. Persistence was associated with higher levels of symptoms and lower IQ in childhood. Persistent individuals had more functional impairment and higher rates of other mental health disorders at age 18 compared to those who remitted. Among individuals with adult ADHD (n=162), 67.9% did not meet criteria for ADHD at any assessment at or prior to age 12. In childhood, individuals with late-onset ADHD showed fewer behavior problems and higher IQ compared to the persistent group; at age 18, they showed comparable ADHD symptoms and impairment and similarly elevated rates of mental health disorders compared to the persistent group. Conclusion and Relevance In this general population cohort, the persistence of ADHD was largely driven by childhood ADHD severity and poorer neuropsychological functioning. Additionally, we identified heterogeneity in the adult ADHD population such that this group consisted of a large late-onset ADHD group with no childhood diagnosis and minimal neuropsychological impairment, and a smaller group with persistent ADHD and associated neuropsychological impairment. Our findings call into question the conceptualization of adult ADHD as a childhood-onset neurodevelopmental disorder.

Investigating late‐onset ADHD: a population cohort investigation

“…(2015) did not show a deficit in IQ (with a mean IQ of 96.94) and the young adult group of Agnew‐Blais et al. (2016) had a mean IQ of 96.12 which was significantly higher than that of their persistent group (89.78). Interestingly, the percentage of our genuine late‐onset group with a household income below the (within‐group) median was 51%, suggesting that this group does not show socioeconomic disadvantage, a factor which is associated with childhood ADHD (Russell, Ford, & Russell, 2015).…”

“…(2015) not finding a link between childhood or adult ADHD status and mood or anxiety problems, Agnew‐Blais et al. (2016) not finding elevated rates of depression and anxiety in their late‐onset ADHD group compared to the persistent group, but Caye et al. (2016) finding elevated rates of mood disorders and anxiety in their young adult ADHD group.…”

“…In this UK longitudinal population‐based cohort, using updated SDQ cut‐points and excluding those with high scores at one time point during childhood, we find lower rates of genuine late‐onset ADHD (0.4%) than other population‐based studies (Moffitt et al., 2015, 2.7%; Agnew‐Blais et al., 2016, 5%; Caye et al., 2016, 7.9%). Indeed, in our sample, 75% (56 of 75 with full data) of those with apparent late‐onset ADHD symptoms were due to potential misclassification once we had taken into account subthreshold or elevated SDQ ADHD scores at least one point in childhood.…”

“…(2016) found that 84.6% of their 18/19 year olds with ADHD did not have a history of childhood ADHD, and Agnew‐Blais et al. (2016) found that 67.5% of their 18 year olds with ADHD had not met criteria for ADHD at any assessment in childhood. Our higher rates of individuals with apparent late‐onset symptoms who we then considered to actually have a childhood history of significant ADHD symptoms (i.e.…”

“…This young adult group had a female preponderance and a range of adverse outcomes including criminality, suicide attempts and comorbidities. Third, a UK twin study (Agnew‐Blais et al., 2016) found that 67% of their young adult ADHD group, as defined at age 18 years again without requiring the ‘age of onset’ criterion, had not met criteria when assessed for ADHD in childhood (at ages 5, 7, 10 and 12 years). Those with late‐onset disorder were more likely to be female, had fewer behaviour problems and higher IQ in childhood than those with persistent ADHD, though were similar in ADHD symptom levels, impairment and mental health comorbidities at age 18 years.…”