Age-Related Changes in the Amygdala From In Utero to Early Childhood: Association With Social and Cognitive Outcomes.

The amygdala is a key element of the limbic system. It is involved in emotional processing controlling responses to social, affective, or motivational stimuli, facilitating interaction with the surrounding environment. Given its importance in typical development, understanding early normative growth patterns in the amygdala can provide insights into the origins of emotional and social behaviors. This study examined age-related differences in amygdala volume from the fetal to early childhood period across six cohorts from in utero to the first 4 years of life, and explored the association with social, cognitive and communication outcomes. Amygdala volumes were analyzed in 471 participants ranging from 27 to 195 weeks postmenstrual age (PMA). The results of the mixed model analyses indicated that volume significantly increased in size with age (t(534) = 7.92, p < 0.001), with the left amygdala demonstrating stronger age-related changes (p < 0.001) and with males showing steeper age-related changes compared to females (p = 0.012). In a subset of participants with developmental outcome data (n = 30), significant associations were observed for the left amygdala, with larger volumes predicting receptive communication (B = -0.02, p = 0.017), including an interaction with sex (B = 0.03, p = 0.028). Additional effects were found for social-emotional (B = -0.03, p < 0.001) and cognitive outcomes (B = -0.02, p < 0.001), with interactions by sex and age (all p < 0.05), whereas no significant findings were detected for the right amygdala. These results characterize age-related changes in amygdala volumes early in development and highlight the role of sex and laterality, while underscoring its importance in social communication during early development.