To explore whether the associations between developmental delays in the first year of life and psychosocial outcomes in preschool children are affected by participation in organized sport.

Data were obtained from the infant cohort of the Growing Up in Ireland project. Parents reported on child development (Ages and Stages Questionnaire) at age 1 year, psychosocial characteristics (Strengths and Difficulties Questionnaire) at ages 3 and 5 years, and engagement in organized sport at age 5 years. Data were analyzed using mixed models.

At age 1 year, 15% of the cohort was classified as having developmental delays. These children exhibited more behavioral difficulties (0.55, ±0.27; mean difference, ±95% confidence limits [CL]) (P < .0001) and fewer prosocial behaviors (−0.54, ±0.11) (P < .0001) at age 3 years. For boys in this group, engagement in sport was associated with a significant decrease in behavioral difficulties between ages 3 and 5 years (−0.44, ±0.39) (P = .03). Compared with those classified as lacking regular engagement (ie, never engaging, or engaging <1 hour/week), the relative effect of sport on changes in behavioral difficulties for boys with developmental delays was statistically significant (0.70, ±0.59) (P = .02). Participation in sport was not associated with significant changes in behavioral difficulties for girls, or a significant change in prosocial behaviors for boys or girls.

Regular participation in sport by boys could attenuate some of the behavioral difficulties associated with early development. Lack of opportunities for engaging in sport could negatively affect boys’ behavioral regulation in the preschool period.