A new study suggests that a child’s genetic propensity for attention‑deficit hyperactivity disorder (ADHD) may be linked to an increased risk of their parents dissolving their partnership. Led by researchers from Purdue University and the University of Oslo, the team analysed how a child’s polygenic index for ADHD relates to parental outcomes such as marriage, additional children and separation.
The work used data from the Norwegian Mother, Father and Child Cohort Study, examining about 40,000 genotyped family trios – mother, father and child – with genetic information collected during pregnancy and at birth. The researchers then matched these genetic profiles with administrative records on marriage, new births and separation from Norwegian registers.
In their analysis, the scientists controlled for both parents’ own polygenic indices to isolate the influence of the child’s genetic profile on the family’s trajectories. For most behavioural and physical health traits, the child’s genetic profile did not predict major parental outcomes. But the ADHD polygenic index stood out as a notable exception.
Specifically, a one standard deviation increase in a child’s ADHD polygenic index was associated with a 7 per cent relative rise in the odds that the parents would separate or divorce. When the data were broken down by sex, the effect was strongest among daughters: an 11 per cent increase in the odds of parental dissolution per 1 SD rise in the child’s ADHD index. Among sons, the increase was under 4 per cent and not statistically significant.
The study also found that socioeconomic status moderated the association. In families with above‑average educational attainment, a one standard deviation increase in the child’s ADHD polygenic index corresponded to a 15 per cent rise in the odds of parental separation, while in lower‑income families the effect did not reach statistical significance.
Maternal age at first birth further influenced the relationship. In families where the mother was older than the median age at her first birth, the ADHD index in the child predicted a 10 per cent increase in the odds of parental separation. In these older‑mother families, there was also a separate finding: a higher anxiety polygenic index in the child was linked to a 10 per cent increase in the odds that the parents would marry after the child’s birth, suggesting older parents might respond to an anxious child with stabilising commitments.
As with all research, the authors note limitations. The study draws on Norwegian data, a country with universal welfare provisions and strong gender equality, which may influence family dynamics differently from other places. The voluntary nature of the cohort means the sample may overrepresent higher socioeconomic groups and underrepresent families facing multiple adversities.
Further caveats concern the genetic measures themselves. Polygenic indices are statistical models rather than direct biological mechanisms, and their predictive power depends on the populations from which they were derived. In this study, indices were based on European‑ancestry data, which may limit generalisability to other ancestral backgrounds. Moreover, these indices capture only a small portion of the genetic influences on ADHD.
The study, authored by Evelina T. Akimova and colleagues, is titled “When children shape their families: Evocative effects analysis of 40,000 trios from the Norwegian Mother-Father-and-Child Study.”
