Researchers at the University of Oregon wanted to answer a question that adoption raises: when a child's stress sensitivity seems high, is it because of genetics passed down by the birth mother, or because of the environment the child grew up in—or both?
They tracked 561 adopted teenagers and gathered information about stress their birth mothers experienced during pregnancy and the life stress their adoptive parents faced. They also measured the teenagers' cortisol levels (a stress hormone) across the day to understand how their bodies regulate stress.
Birth mother stress leaves a biological mark, even years later
The study found something striking: teenagers whose birth mothers had experienced significant life stress during pregnancy showed different stress hormone patterns than other teens. Specifically, their cortisol didn't drop as much as it should through the day—a sign their stress-response system works differently. This connection held even though these children had been adopted and raised by different families, suggesting prenatal stress exposure matters beyond just genes.
Your stress now can amplify or soften your child's inherited pattern
Here's where adoptive parents came in: the researchers discovered that when adoptive parents themselves experienced high stress, the effects of prenatal stress became even stronger in their teenagers. The opposite was also true—when adoptive parents had lower stress levels, they seemed to buffer against some of the biological effects passed down prenatally. This suggests that a calm, stable home environment can genuinely reduce how strongly a child's inherited stress sensitivity shows up.
What this means for pre-nursery parents
While this study focused on teenagers adopted as infants, it underscores something that matters for all young children: parental stress is not just about feeling overwhelmed yourself. Your stress levels interact with your child's biology in measurable ways. The good news is that managing your own stress appears to be one of the most direct ways you can support your child's developing stress system.
- Prioritise stress management for yourself—your calm presence genuinely shapes how your young child's body learns to handle stress.
- Build routines that feel predictable and safe at home; stable environments appear to help children regulate their stress responses more effectively.