Genome-wide association studies of infant temperament reveal genetic links with later life outcomes

We conducted genome-wide association studies on infant temperament – Emotionality, Activity, Shyness and Sociability (N=43,963-72,663) - and meta-analysed the results. We studied the second and third years after birth and a cross-infancy average. Cross-age SNP heritabilities were 6.79% (SE=1.06%) for Emotionality, 9.55% (SE=1.28%) for Activity, 15.26% (SE=1.54%) for Shyness and 3.42% (SE=1.08%) for Sociability. Ten independent genome-wide significant loci were discovered; two colocalized with eQTLs for RHEBL1 (Posterior probability (PP)=0.93, associated with Activity) and MR1 (PP=0.99, associated with Emotionality), both expressed in adult cortex. Genetic correlations were observed between infant Emotionality and adult Neuroticism, infant Activity and ADHD, infant Sociability and Autism, and infant Shyness and adult Extraversion. Multi-ancestry analyses (N=56,083-78,894) gave similar results to European-ancestry analyses. Infant temperament is influenced by common genetic variation and shows genetic continuity with later life outcomes.