Attention deficit/hyperactivity and comorbid symptoms in preschoolers: Differences between subgroups in neuropsychological basic deficits.


Background: There is wide agreement on the heterogeneity of attention deficit/hyperactivity disorder (ADHD). Subgroups with specific comorbid problems, neuropsychological deficits, and developmental trajectories that start in preschool years have been assumed. We analyze whether corresponding subgroups at risk for ADHD development can be identified in a preschool sample and whether these subgroups show the assumed neuropsychological deficits. Methods: The study sample consisted in 141 preschool children (3-6 years; 68 boys), including 41 children at risk for ADHD development (because of high ADHD symptoms or first-degree relatives with an ADHD diagnosis). Parent- and teacher-reported symptoms of ADHD, ODD/CD, and anxiety/depression were assessed. Cluster analyses were conducted on the continuous symptom scores. Inhibitory control and delay aversion were measured by six neuropsychological tasks. Results: Cluster analyses resulted in four groups. Two of these groups showed high ADHD symptoms – one showing multiple comorbid symptoms, one showing hardly any further symptoms. The other two groups were characterized by no problems and by some sensorimotor deficits. A priori contrasts revealed that the ‘high comorbidity’ cluster showed the worst inhibitory control performance while the ‘pure ADHD symptoms’ cluster showed the highest delay aversion. Conclusion: The ADHD-symptom clusters matched types that have been proposed in recent models. This description might help to identify different ADHD-related pathways in future longitudinal research.