Relationship between having siblings and developmental status: A cross-sectional study in a cohort of 2-year-old Iranian children.

Aims: Dealing with the aging population crisis is one of the priorities of research and intervention in Iran, which requires scientific and comprehensive persuasion of families to have more children. This study investigated the relationship between having siblings and child' developmental status.

Methods and materials: Using the data from the PERSIAN birth cohort study, 611 two-year-old children who were residents of Semnan were investigated. The studied information included the gender of the child, the number of siblings, and the developmental test score of the child at the age of two. The assessment of the child's development was performed using the Ages and Stages Questionnaires (ASQ).

Results: Among 294 girls and 317 boys, 352 (57.6%) had no siblings, and the remaining group had between 1 and 5 siblings. The mean (± standard deviation) of the developmental score in children who had siblings (281 ± 23) was higher than children who did not have siblings (278 ± 21) (Cohen's d = .14, P = .029). This difference was also true in the field of large movements (P = .001). Adjusting for gender of child, age, and education of mother only the relationship between large movements and having siblings remains significant (P = .015).

Conclusions: Having siblings may help a child develop social and personal skills probably by increasing family social interaction. Emphasizing the positive impact of having brothers and sisters on a child's growth and development can be a motivating factor for having more children in the family.