What is already known on this topic

While many children with attention-deficit hyperactivity disorder (ADHD) will experience remission of the disorder,1 a substantial proportion will continue to have ADHD and associated impairments into adolescence and adulthood.2 Those with persistent ADHD have poorer outcomes later in life in some domains, including more emotional and substance use problems, compared to those whose ADHD remits.3 Previous studies have identified factors such as childhood ADHD severity, comorbidities4 and IQ5 as associated with ADHD persistence.

Methods of the study

The Multimodal Treatment Study of Children with ADHD (MTA) is one of the largest ADHD treatment studies to date. The original trial assigned medication management, intensive behavioural treatment, combined medication and behavioural treatment or community care for 14 months. The current paper includes follow-up of over 450 participants up to 16 years after baseline (mean age 24.7 years). Logistic regression was used to identify childhood factors associated with ADHD persistence in young adulthood, assessed with Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria. An initial series of regression models assessed predictors of persistence adjusting for sex, age at baseline and MTA site; a second series of models additionally adjusted for baseline ADHD symptom level to identify predictors of persistence independent of childhood ADHD severity. Potential predictors included characteristics of the child, such as IQ (assessed by the Wechsler Intelligence Scale for Children, Third Edition) and childhood comorbidity (number of childhood diagnoses), as well as family characteristics, such as parental psychopathology (number of parental mental health problems), socioeconomic status and parenting style. Sensitivity analyses varying the definition of ADHD persistence explored the robustness of these predictors.

What this paper adds

• Childhood comorbidity (OR 1.15, SE 0.07, p=0.035) and parental mental health problems (OR 1.35, SE 0.09, p=0.004) were associated with ADHD persistence.

• These predictors remained significantly associated across a range of persistence definitions, including ADHD diagnoses with and without an impairment criterion, and using both a dichotomous diagnosis and continuous symptom scores.

• Importantly, parental mental health problems were associated with a 28% increased risk of persistence even when adjusting for baseline ADHD symptoms, suggesting they are predictive of later ADHD over and above their association with baseline ADHD severity.

• These findings are identified in a sample with ADHD diagnoses based on both parent and self-report, using diagnostic criteria that were varied to assess the robustness of findings, at a follow-up point that falls solidly within young adulthood. The authors examined a wide range of potential predictors of persistence, including aspects of the family environment such as parent–child relationships and parenting styles.

Limitations

• It remains to be seen whether these predictors of persistence in young adulthood would also characterise persistence of ADHD to later ages, such as into mid-life.

• The MTA study was focused on children with combined-type ADHD who were recruited from sources including mental health settings and paediatric referrals, so these participants may have more severe ADHD, possibly leading to a higher overall rate of persistence and potentially different predictors of persistence than one might find in a more general population, community-based sample.

What next in research

• A future goal in predicting persistence of ADHD could be to combine factors associated with persistence identified by prospective studies into a risk score that could have clinical utility for identifying individuals at increased risk for ADHD persistence.

• Recent research suggests that ADHD polygenic risk score can predict persistence6; how genetic risk fits in with these other risk factors of persistence can be further explored in future research.

Do these results change your practices and why?

Yes. Childhood ADHD severity, childhood comorbidity, and parental mental health problems offer targets for intervention to reduce ADHD persistence. These findings suggest that a holistic treatment approach, in which clinicians both treat childhood ADHD symptoms as well as focus on childhood comorbidities and parental mental health problems, may be needed to affect a long-term change in the risk of ADHD persistence into young adulthood.