Persistence, Remission and Emergence of ADHD in Young Adulthood: Results from a Longitudinal, Prospective Population-Based Cohort

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.