In a study conducted in the Netherlands, results demonstrated that ADHD is a persisting disorder, with high symptom severity and family history of ADHD representing significant risk factors.
This 6-year follow-up study of subjects previously enrolled in the Dutch part of the International Multicenter ADHD Genetics (IMAGE) study conducted in 2003–2006 examined the outcomes of combined-subtype ADHD (C-ADHD) in late adolescence/early adulthood with respect to persistence* and comorbidity rates, symptom severity and overall functioning. In addition, childhood predictors of symptom severity and overall functioning were investigated, and the effects of continuing pharmacological treatment were assessed.
Of the 459 children with C-ADHD at baseline, 333 children had available information at follow-up (mean age 17.36 years): 86.5% of participants had persistent ADHD, 51.4% had C-ADHD, 39.6% had ADHD inattentive type, 9.0% had hyperactive/impulsive type, 8.4% had a subthreshold diagnosis and 5.1% no longer presented with the disorder.
Compared with baseline, the prevalence of oppositional defiant disorder and conduct disorder at follow-up was significantly lower (58.0% vs 30.8% and 18.9% vs 6.6%, respectively). The rates of tic, mood and anxiety disorders at follow-up were estimated at 2.1%, 1.8% and 2.5%, respectively. At follow-up, 90.9% of participants had received pharmacological treatment compared with 78.8% at baseline, and 48.5% still experienced functional impairments, as measured using the Schedule for Affective Disorders and Schizophrenia rating scale for school-aged children.
Baseline predictors of higher current symptom severity were: positive parental ADHD diagnosis, higher symptom severity and parent-reported impairment. Poorer overall functioning was associated with younger age, higher ADHD severity and higher impairment per parents’ assessment at baseline. As evaluated at follow-up, pharmacological treatment did not yield beneficial effects on ADHD symptom severity and overall functioning.
The sample size used in this study may have been relatively small for the analyses performed. In addition, the inclusion of participants from Caucasian origin only and the restriction of baseline ADHD diagnosis to the combined ADHD subtype preclude the generalisability of the results to the general population and to other ADHD subtypes. Nevertheless, the findings confirmed the persistent nature of C-ADHD and revealed factors with predictive power of its outcomes in late adolescence/early adulthood.
*Persistent participants met full Diagnostic and Statistical Manual of Mental Disorders – 5th Edition (DSM-5TM) criteria for C-ADHD at baseline, and full DSM-5TM criteria for ADHD regardless of subtype at follow-up. Patients with subthreshold persistence met full DSM-5TM criteria for C-ADHD at baseline, but ADHD diagnosis at follow-up met subthreshold criteria (for participants aged <18 years: <6 symptoms of inattention and hyperactivity/impulsivity, but ≥4 symptoms of inattention and/or hyperactivity/impulsivity at follow-up; for participants aged ≥18 years: thresholds were 5 and 3 symptoms, respectively.)
van Lieshout M, Luman M, Twisk JWR, et al. A 6-year follow-up of a large European cohort of children with attention-deficit/hyperactivity disorder-combined subtype: outcomes in late adolescence and young adulthood. Eur Child Adolesc Psychiatry 2016; 25: 1007-1017.