Adoption and development from infancy to adulthood: A systematic review of longitudinal studies and future directions

Research suggests considerable developmental catch-up among adopted children who experienced early adversity across various domains, yet a substantial subgroup continues to exhibit elevated socio-emotional difficulties. Longitudinal studies can provide critical insights into the mechanisms underlying this ongoing vulnerability, yet no systematic review has been conducted to synthesize these findings. This systematic review identified 16 longitudinal studies (<i>N</i> = 3,073 adoptees) through searches in PsycINFO, PubMed, Scopus, and Web of Science, all of which followed children adopted before the age of six into adolescence or adulthood, with an average follow-up period of 10 years. Due to significant heterogeneity across study designs, samples, and measures, a meta-analysis was not feasible; therefore, adoptees' outcomes and developmental pathways are synthesized narratively. Early adversity and developmental difficulties most frequently predicted later socio-emotional and behavioral outcomes, with some evidence pointing to genetic, epigenetic, and gene-environment interaction effects. Early difficulties may have cascading consequences across multiple developmental domains. Yet, the small number of longitudinal studies and their heterogeneity limits conclusive understanding of developmental pathways. Recommendations are made to inform and strengthen future research efforts.