Meta-analysis of Longitudinal Total Brain Volume Trajectories in Autism

Early brain overgrowth is well-documented in autism spectrum disorder (ASD); however, longitudinal brain development has not been systematically charted. We performed a meta-analysis of longitudinal total brain volume (TBV) trajectories in ASD compared to controls, including 6 studies, 453 ASD and 3,510 controls aged 6 months to 18 years. Cross-sectional TBV was larger in ASD than controls (Hedges’ g = 0.22, p = 0.014). Meta-regressions showed larger TBV was specific to early childhood, with reduced TBV in late adolescence in ASD (F(2, 13) = 37.51, b=-0.06, p <0.001). Longitudinally, TBV growth was reduced over time in ASD versus controls (g=-0.09, p = 0.06). In summary, TBV alterations in ASD are age dependent, it remains unclear whether alterations persist into adulthood due to a lack of studies beyond age 18.