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A new study published in the Proceedings of the National Academy of Sciences (PNAS) challenges the traditional view that influence within families flows only from parents to children. The research was led by former LCDS researcher Dr Evelina Akimova, now Assistant Professor of Sociology at Purdue University, and co-authored by Professor Melinda C. Mills, Director of the Leverhulme Centre for Demographic Science (LCDS) as part of Mills’ ERC Advanced Grant. The research shows how genetic influences can operate differently than has been examined before, by demonstrating that children’s genetically influenced characteristics may in fact shape important family outcomes over time.
The researchers analysed data from nearly 40,000 Norwegian families to investigate whether children’s genetic predispositions for a range of health, behavioural, and cognitive traits were associated with major family outcomes, including whether parents had more children, married, or separated. By combining genetic information from mothers, fathers, and children, the team was able to distinguish children’s own genetic makeup from those inherited from their parents, providing a new way to examine how children may influence family life.
For most of the traits examined—including anxiety, depression, autism, educational attainment, cognitive performance, asthma, and allergies—the researchers found no association with the family outcomes they studied. One exception emerged: children with a higher genetic propensity, for attention-deficit/hyperactivity disorder (ADHD), were associated with a 7% higher likelihood of parental separation. The association was stronger among families with daughters, at 11%; families with higher socioeconomic status, at 15%; and families in which mothers were older at the birth of their first child, at 10%. The authors stress that this does not mean that a child’s genetic makeup cause parents to separate. Rather, characteristics associated with ADHD, such as hyperactivity, impulsivity, and difficulties with emotional regulation, may shape family dynamics alongside the many social, economic, and environmental factors that influence family life.
“Parents undoubtedly play a fundamental role in shaping children’s lives, but this study flips the focus and looks at how children can influence their parents,” says Professor Melinda Mills. “By combining demographic and genetic data, we can begin to understand more precisely how children’s personal and genetic characteristics may influence the relationships and environments around them. This helps us to move beyond viewing parents and intergenerational transmission as a one-way influence.”
The findings contribute to a growing body of research showing that family relationships are multidirectional. By integrating demographic methods with population genetics and biosocial family data, the study offers a new perspective on how family dynamics unfold over time and demonstrates the value of combining different forms of data to better understand the complex processes that shape people’s lives.
Read the study: Proceedings of the National Academy of Sciences
"When children shape their families: Evocative effects analysis of 40,000 trios from the Norwegian Mother, Father and Child Cohort Study", has published and is now available at: www.pnas.org/doi/10.1073/pnas.2532642123 with DOI number 10.1073/pnas.2532642123.
For further information contact: melinda.mills@demography.ox.ac.uk
About the funders:
During the writing of this paper, Dr Akimova and Professor Mills were supported by Mills’ ERC Advanced Grant CHRONO (ERC AdG; 835079) and a Leverhulme Trust Large Centre Grant LCDS "Leverhulme Centre for Demographic Science" (RC-2018-003) and Mills also by European Social Science Genetics Network ESSGN(HORIZON-MSCA-DN-2021; (101073237), Economic and Social Research Council/ United Kingdom Research and Innovation Connecting Generations (ES/W002116/1) and Einstein Foundation Berlin (EZ-2019-555-2). Mills’ strand of interdisciplinary work combines genetics, demography and social science to better understand family processes and human behaviour.
Frequently Asked Questions: When Children Shape Their Families
Q: What is the main focus of this study?
A: The study investigates whether children play a role in shaping their family's demographic future—such as whether their parents stay together, get married, or choose to have more children. Traditionally, family outcomes are viewed as being driven by parental choices or structural socioeconomic conditions. This study flips the script to see if a child's genetic predispositions for certain traits indirectly influence their parents' relationship trajectories.
Q: What is the most significant finding?
A: While the researchers found limited evidence that most childhood traits influence major family demographic shifts, there was one glaring exception: ADHD. Children who carry a higher genetic likelihood (Polygenic Index) for Attention-Deficit/Hyperactivity Disorder (ADHD) were linked to a significantly increased risk of their parents separating or divorcing. Overall, a higher ADHD index in a child predicted a 7% increased risk of parental separation per standard deviation.
Q: Did the likelihood of parental separation vary depending on the type of family?
A: Yes. The association between a child's ADHD genetics and parental separation was not uniform; it was heavily influenced by demographics. The researchers found the effect was much stronger in:
- Higher socioeconomic status (SES) families: 15% increased risk of dissolution per standard deviation. (The researchers note that SES was the main source of variation).
- Families with daughters: 11% increased risk.
- Older mothers (at first birth): 10% increased risk.
Q: What do the researchers mean by "evocative effects"?
A: In behavioural genetics, an "evocative gene-environment correlation" occurs when an individual's inherited traits trigger or evoke a specific response from their environment. In the context of this study, it means that a child’s genetically influenced behaviours or needs (such as those associated with ADHD) evoke a stress or response in the family environment, which can ultimately impact whether the parents stay together.
Q: How was the study conducted?
A: The research team utilized data from the Norwegian Mother, Father and Child Cohort Study (MoBa). They analysed a massive dataset of 40,000 "trios"—meaning they looked at the genetic data of the mother, the father, and the child together.
Because children inherit their genetics from their parents, the researchers statistically controlled for the parents' own Polygenic Indices. This allowed them to isolate the unique "child-to-parent" effect to see how the child's genetics alone predicted future parental behaviours (fertility, separation, and marriage).
Q: Why is this research newsworthy?
A: It challenges the traditional "top-down" view of family dynamics. Usually, demographers look at how a parent's education, wealth, or mental health shapes the child. This study proves that family dynamics are a two-way street. It provides a new genetically-informed evidence that children are not just passive recipients of their environment; their traits and needs actively shape the life courses of their parents.
