A large Swedish study published in The BMJ today suggests that an improved early home environment can have lasting positive effects across generations.
Children of parents with psychiatric or behavioural issues who were adopted before age 10 into families with better home environments, showed improved adult psychosocial outcomes, including fewer criminal convictions and higher educational achievements, than their unadopted siblings.
Some of these advantages also extended into the next generation.
The researchers emphasise that these findings do not advocate adoption as a policy intervention. Instead, they support the idea that improving early life conditions "might exert durable effects across psychiatric, educational, and socioeconomic domains, even in societies with relatively robust welfare."
Experimental studies suggest that improving early life environments can benefit later cognitive, educational, and behavioural outcomes. But evidence is limited as to whether improved conditions during childhood have long term effects after taking account of other family factors, and whether benefits extend to the next generation.
To address this, researchers used Swedish registry data to identify two large sibling groups (full siblings and maternal half siblings) born between 1950 and 1980 to parents with a history of psychiatric diagnosis, suicide, or criminal behavior.
Both groups spanned three generations and were discordant for adoption before age 10, meaning that one sibling was adopted into non-relative families while the other remained in the biological family home.
The researchers then examined the extent to which the adopted siblings displayed improved functioning in adulthood compared with their siblings who had remained in the biological family home, and if these improvements transferred to the next generation (offspring born 1965-2020).
In total, 4,254 full siblings and 7,796 maternal half siblings, who were or were not adopted before age 10 were included in the analysis.
Adopted individuals showed a lower risk of psychiatric disorders (30% v 36% among non-adopted siblings), criminal convictions (26% v 34%), and receiving social welfare (38% v 49%).
They also showed higher mean intelligence scores (4.5 v 3.8) and non-cognitive skills scores (4.8 v 3.9) and were more likely to have attended university (26% v 15%).
These patterns held across both full sibling and maternal half sibling samples.
The offspring of adopted individuals also displayed modestly higher psychosocial functioning than their cousins (eg, 30% v 32% with psychiatric disorders), although these associations were weaker and less precise.
This is an observational study, so can't establish cause and effect, and the authors acknowledge that factors such as timing of adoption, child characteristics, and socioeconomic differences between biological and adoptive families could have influenced the results.
Nevertheless, the study was large with a long follow-up period, and captured a wide range of health and academic outcomes across three generations.
As such, the authors conclude: "Early adoption into a family with favourable home environment conditions was associated with moderate, enduring benefits across psychiatric, social, and cognitive outcomes, extending into the next generation. These results highlight the potential for environmental improvements during childhood to mitigate intergenerational disadvantage."
These findings confirm that early-life environments shape long term mental health, functioning, and life chances, particularly for children growing up in adversity, says US based researcher Anna Chorniy in a linked editorial.
However, she argues that adoption itself is not a scalable solution, and improving children's environments through greater stability, resources, and caregiver support may yield lasting benefits.
Chorniy emphasises the need to understand the underlying mechanisms and translate these insights into concrete, scalable policies and interventions that can support children and families more broadly.
