The contribution of common and rare genetic variation to emotional and behavioural symptoms in childhood and adolescence

AI Summary

Both common polygenic variation and rare deleterious coding variants independently contribute to childhood internalising and externalising symptoms.
Polygenic indices for ADHD and externalising behaviour showed the largest, stable associations with externalising symptoms across ages 5 to 17.
Higher exome wide burden of rare deleterious variants associated with increased internalising and externalising symptoms; within family models suggested some direct genetic effects.

AI Summary

We analysed genotype array (n = 4709-6687) and exome sequence data (n = 4500-5424) from the Millennium Cohort Study (MCS) and Avon Longitudinal Study of Parents and Children (ALSPAC) to assess the contribution of common variants and rare deleterious coding variants to internalising and externalising symptoms across development.

A higher exome-wide burden of deleterious rare variants was associated with increased externalising and internalising symptoms (β = 0.04-0.06, p-adj<0.03); within-family models indicated direct genetic effects on externalising in MCS (β = 0.07; p < 0.05, p-adj>0.05) and on internalising symptoms in ALSPAC (β = 0.12, p-adj<0.02).

This study shows that early-life mental health is influenced by both common and rare genetic variation, with several associations explained by direct genetic effects.

Basic summary

Mol Psychiatry. 2026 Sep 11. doi: 10.1038/s41380-026-03851-6. Online ahead of print.

ABSTRACT

Genetic factors influence vulnerability to common mental health conditions, but their role in early-life mental health remains understudied. We analysed genotype array (n = 4709-6687) and exome sequence data (n = 4500-5424) from the Millennium Cohort Study (MCS) and Avon Longitudinal Study of Parents and Children (ALSPAC) to assess the contribution of common variants and rare deleterious coding variants to internalising and externalising symptoms across development. In longitudinal analysis spanning ages 5-17 years, we identified several associations between common genetic variation, indexed by polygenic indices (PGIs), and both symptom domains that generally remained stable across development. Effect sizes were modest, with the largest estimates observed for PGIs for attention deficit hyperactivity disorder (ADHD) and externalising behaviour with externalising symptoms (β = 0.13-0.18; p-adj<3.5×10⁻²⁹). Evidence for direct genetic effects was strongest for externalising symptoms, including for associations with the ADHD and externalising behaviour PGIs. Concordant results were observed in the Born in Bradford cohort. A higher exome-wide burden of deleterious rare variants was associated with increased externalising and internalising symptoms (β = 0.04-0.06, p-adj<0.03); within-family models indicated direct genetic effects on externalising in MCS (β = 0.07; p < 0.05, p-adj>0.05) and on internalising symptoms in ALSPAC (β = 0.12, p-adj<0.02). Common and rare genetic variants contributed independently, jointly explaining 2% of the variance in internalising and 5-7% in externalising symptoms. This study shows that early-life mental health is influenced by both common and rare genetic variation, with several associations explained by direct genetic effects.

PMID:42728315 | DOI:10.1038/s41380-026-03851-6

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