Early child-rearing conditions may improve psychosocial outcomes in adopted children compared to unadopted biological siblings

1. Adopted individuals who experienced improved environmental conditions had better long-term psychosocial outcomes than their unadopted biological siblings, with some advantages also observed in the next generation.

Evidence Rating Level: 2 (Good)

Improving home environments during early life can benefit later cognitive, educational, and behavioural outcomes. However, the long-term protective effect of child-rearing conditions and whether benefits extend to the next generation is unclear. This study thus examined whether improved home environment conditions through early adoption reduced long-term psychosocial risks and provided intergenerational benefits. This population-based adoption-discordant sibling comparison study used a Swedish register of births between 1950 and 1980, with follow-up to 31 December 2020. Two samples of sibling pairs were included: one with full siblings and one with maternal half-siblings who were or were not adopted before age 10. Biological parent or parents of these siblings had a history of a psychiatric diagnosis, suicide (attempt or death), or criminal behaviour. Offspring of these siblings were followed to assess intergenerational spillover effects. The main outcomes were psychiatric diagnoses, long-term unemployment, receipt of social welfare, highest attained criminal convictions, and, among men, non-cognitive skills and general intelligence assessed at military conscription. In total, 4254 full siblings (2719 home-reared, 1535 adopted) and 7796 maternal half siblings (5006 home-reared, 2790 adopted) were included in the study. Compared with their biological full siblings who were raised by the biological parents, the adopted individuals showed a lower risk of psychiatric diagnosis (29.8% v 36.1%; hazard ratio [HR], 0.70; 95% CI, [0.63 to 0.78]), criminal conviction (26.1% v 34.0%; HR, 0.66; 95% CI, [0.60 to 0.74]), and receiving social welfare (37.8% v 48.5%; HR, 0.63; 95%CI [0.57 to 0.70]). Adopted individuals also showed higher non-cognitive skills scores (mean 4.8 v 3.9), general intelligence scores (mean 4.5 v 3.8), and were more likely to have attended university (26.0% v 15.2%). Results were similar in the maternal half-sibling sample. Among the offspring of adopted individuals (n=2750), psychosocial functioning was modestly higher than that of their cousins (eg, 29.6% v 32.3% with psychiatric disorders), although the hazard ratios were not significant. Overall, this study found that adopted individuals who experienced improved environmental conditions had better long-term psychosocial outcomes than their unadopted biological siblings, with some advantages also observed in the next generation. These findings support possible intergenerational benefits of improved early rearing conditions.

Click here to read this study in the BMJ

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