Horizontal bars reflect significant group differences between CHD8 (red, left), Target (pink, middle), and Other Gene (grey, right) groups. Distribution of head circumference z-scores indicates larger head sizes for the CHD8 and Target groups relative to the Other Gene group. Horizontal dashed lines indicate clinical criterion for macrocephaly (z-score = 2) and microcephaly (z-score = −2). Solid horizontal lines indicate significant group differences with Bonferroni correction applied.