Deficits in executive functions (EF) have been found in school-age children and adolescents with externalizing behavior disorders. Present meta-analysis was carried out to determine whether these EF impairments can also be found in preschool children with externalizing behavior problems. Twenty-two studies were included with a total of 4021 children. Four separate meta-analyses were conducted, concerning overall EF, working memory, inhibition and cognitive flexibility. A medium correlation effect size was obtained for overall EF (ESzr = 0.22) and for inhibition (0.24), whereas a small effect size was found for working memory (0.17) and for cognitive flexibility (0.13). Moderator analyses revealed a stronger effect for older preschoolers compared to younger preschoolers, and for children from referred samples compared to community samples. These results show that EF, especially inhibition, is related to externalizing behavior problems already in preschool years.

Clinically diagnosed preschool children with ADHD showed robust inhibition deficits, whereas preschool children with DBD showed impaired inhibition especially where motivational incentives were prominent. Severity of inhibition impairment in the comorbid group was similar to the ADHD group.

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In this longitudinal study, we examined the stability of the association between executive functions and externalizing behavior problems, and the developmental change of executive functions in a predominately clinically diagnosed preschool sample (N = 200). Inhibition and working memory performance were assessed three times in 18 months. Across time, poorer inhibition performance in young children was associated with attention deficit hyperactivity disorder (ADHD) and disruptive behavior disorders (DBD), and poorer working memory performance was associated with ADHD. Inhibition and working memory performance increased over time, especially in the early preschool period. The improvement of inhibition performance was more pronounced in the clinically diagnosed children compared to the TD children.