Table 2.

Corpus callosum volumes (cm³) at baseline and 2-year follow-up.

	Time 1				Time 2				Age Cohen’s d	Dx. Cohen’s d	Age X Dx. Cohen’s d
	Autism (N=22)		Controls (N=23)		Autism (N=19)		Controls (N=19)
	M	SD	M	SD	M	SD	M	SD
TBV	1349	119	1350	103	1347	126	1340	97	.17	.06	.12
TWM	482	42	493	47	491	51	496	37	.34	.34	.33
Total CC	5.83	1.04	6.63	.88	6.24	1.05	6.82	.94	1.82*	.49*	.30
Rostrum	.06	.06	.08	.05	.09	.05	.08	.05	.40	.11	.04
Genu	1.62	.36	1.75	.27	1.71	.35	1.83	.33	.87*	.03	.09
Rostral Body	.65	.20	.75	.11	.72	.19	.73	.12	.32	.64*	.67*
Anterior Mid-Body	.59	.17	.68	.11	.67	.16	.71	.12	1.40*	.31	.05
Posterior Mid-Body	.53	.14	.61	.10	.61	.13	.65	.10	1.44*	.24	.16
Isthmus	.55	.16	.64	.19	.61	.18	.64	.20	.41	.40	.30
Splenium	1.77	.38	2.07	.47	1.89	.37	2.14	.45	.94*	.22	.07

Note.

^{^}p<.10,

^*p<.05.

TBV= Total Brain Volume, TWM= Total White Matter. Age = Age Main Effect, Dx. = Diagnosis Main Effect, Age X Dx. = Interaction of Age and Diagnosis; Main effects and interactions for CC volumes do not include TWM as a covariate; d= Cohen’s d. Positive effect sizes (d) indicate increasing volume with age (Age), lower volume in the autism group (Dx.), and larger increases in volume with age in the autism group relative to the controls (Age X Dx.). All volumes are in cm3.