FIGURE 2.

Amygdala growth between 6 and 24 months in infants at high or low likelihood for ASD who did or did not develop ASD and infants with fragile X syndrome^a

^a ASD=autism spectrum disorder; FXS=fragile X syndrome; HL-ASD=infants at high likelihood for ASD who were later diagnosed with ASD; HL-negative=high-likelihood infants who were negative for ASD; LL-negative=low-likelihood infants who were negative for ASD. Infants who developed ASD had faster amygdala growth between 6 and 24 months; there were no group differences at 6 months, followed by significantly larger amygdala volume in the ASD group at 12 and 24 months, compared with all other groups; there was a significant group-by-age interaction (p<0.0001). Plots of the model-adjusted least-squares means are overlaid onto the raw data points of all participants. Percent differences in least-squares means are in relation to the LL-negative group. Effect sizes for the HL-ASD group relative to the LL-negative group: d=0.15 at 6 months; d=0.56 at 12 months; d=0.40 at 24 months. (Note that the LL-negative (blue) and HL-negative (purple) lines are overlapping.) Error bars indicate standard error of the mean. Asterisks indicate p values (corrected) compared with all other groups; n.s.=not significant.

*p<0.05. **p<0.005.