Developmental milestones in early childhood and genetic liability to neurodevelopmental disorders.

Researchers studied over 25,000 Norwegian children to see if genes linked to autism, ADHD, and schizophrenia affect when babies reach early milestones like walking and talking. They found that children with genetic risk for ADHD walked slightly earlier, while girls with autism genetic risk walked slightly later. No clear patterns emerged for talking milestones. The effects were small but real, suggesting genetics may influence when children reach motor milestones.

This large-scale Norwegian cohort study (n=25,699) investigated associations between genetic liability to neurodevelopmental disorders and early developmental milestones. Researchers calculated polygenic scores for autism, ADHD, and schizophrenia, then examined relationships with motor and language milestone attainment. Key findings showed ADHD genetic liability was associated with earlier walking in both sexes, while autism genetic liability was linked to later walking in females only. No robust associations were found between any neurodevelopmental genetic liability and language milestone attainment.

Effect sizes were small but statistically significant, suggesting genetic factors influencing neurodevelopmental conditions may subtly affect early motor development timing in the general population.

Findings suggest early motor milestones may reflect underlying genetic neurodevelopmental liability, particularly for ADHD and autism. However, small effect sizes limit immediate clinical utility. Sex differences in autism associations warrant further investigation for understanding developmental trajectories.

Effect sizes were small, limiting practical significance. Study relied on maternal reports which may introduce bias. Polygenic scores explain only small portions of genetic liability. Associations may not translate to clinical diagnostic utility.

Timing of developmental milestones, such as age at first walking, is associated with later diagnoses of neurodevelopmental disorders. However, its relationship tofor neurodevelopmental disorders in the general population is unknown. Here, we investigate associations between attainment of early-life language and motor development milestones and genetic liability to autism, attention deficit hyperactivity disorder (ADHD), and schizophrenia. We use data from a genotyped sub-set (= 25699) of children in the Norwegian Mother, Father and Child Cohort Study (MoBa).

We calculate polygenic scores (PGS) for autism, ADHD, and schizophrenia and predict maternal reports of children's age at first walking, first words, and first sentences, motor delays (18 months), and language delays and a generalised measure of concerns about development (3 years). We use linear and probit regression models in a multi-group framework to test for sex differences. We found that ADHD PGS were associated with earlier walking age (= -0.033,< 0.001) in both males and females. Additionally, autism PGS were associated with later walking (= 0.039,= 0.006) in females only.

No robust associations were observed for schizophrenia PGS or between any neurodevelopmental PGS and measures of language developmental milestone attainment. Genetic liabilities for neurodevelopmental disorders show some specific associations with the age at which children first walk unsupported. Associations are small but robust and, in the case of autism PGS, differentiated by sex. These findings suggest that early-life motor developmental milestone attainment is associated with genetic liability to ADHD and autism in the general population.