Examining the heritability of functional brain networks in adolescence

Understanding the mechanisms underlying mental illness requires disentangling the roles of genetic and environmental factors. The brain has been proposed as a key intermediate biomarker linking these factors, yet the extent to which genetics shapes adolescent brain function remains elusive. Using data from the ABCD study (5,247 unrelated, 330 dizygotic, 248 monozygotic twin participants), we estimated heritability of functional connectivity and topography using both SNP and twin data. SNP heritability, calculated using genetic correlation and the AdjHE-RE estimator, was low for connectivity (median = 2e-10% Gordon, 5.8e-7% probabilistic) and topography (max = 2%). Twin-based ACE models replicated prior literature (median = 8.9e-6% Gordon, 6% probabilistic connectivity, 27% topography). These results indicate that additive genetic effects have minimal influence on adolescent functional brain features, emphasizing the need to integrate environmental factors when studying the development of functional brain networks and their relevance to mental health.