Are subsyndromal manifestations of attention deficit hyperactivity disorder morbid in children? A systematic qualitative review of the literature with meta-analysis.

We conducted a qualitative review (n = 15 manuscripts) and meta-analysis (n = 9 manuscripts) of the extant literature to evaluate the prevalence and morbidity of subthreshold Attention Deficit Hyperactivity Disorder (ADHD). Our qualitative review showed that a sizable minority (mean: 17.7%) of clinically referred and non-referred children met a priori definitions of subthreshold ADHD. Those affected exhibited significantly higher rates of family dysfunction, cognitive impairment, executive dysfunction, interpersonal and school deficits, temperament problems, psychiatric comorbidity, and juvenile delinquency compared to children with no ADHD symptoms. These deficits were highly consistent with those observed in children with full threshold ADHD. These findings indicate that children with subthreshold ADHD symptoms are at significantly greater risk for negative outcomes in a wide range of non-overlapping functional domains worthy of further clinical and scientific consideration.