Table 1.

Demographics (at T1, unless otherwise specified) and total brain measures.

Measure	Decreasers n = 53	No-changers n = 42	Increasers n = 66	Test Statistic (autistic subgroups)		Autism N = 161	Neurotypicals N = 172	Test statistic (autisticSD vs. neurotypical participants)
ADI social	16.21 ± 7.3	17.93 ± 5.7	16.29 ± 6.9 (65)	F2,157 = 0.962	p = 0.384	1.69 ± 6.7 (160)
ADI comm	13.26 ± 5.8	14.64 ± 5.7	12.89 ± 5.6 (65)	F2,157 = 1.258	p = 0.287	13.48 ± 5.7 (160)
ADI RRB	3.98 ± 2.8	5.17 ± 2.6	3.52 ± 2.2 (65)	F2,157 = 5.459	p = 0.005	4.11 ± 2.6 (160)
Age (Years)	17.07 ± 6.7	14.68 ± 4.3	18.10 ± 4.7	F2,158 = 5.337	p = 0.006	16.87 ± 5.5	16.35 ± 5.7	F1,331 = 0.727	p = 0.394
CSS total	5.35 ± 2.9 (52)	5.60 ± 2.8 (40)	4.83 ± 2.5 (63)	F2,152 = 1.090	p = 0.339	5.20 ± 2.74 (155)
CSS SA	6.02 ± 2.8 (52)	6.25 ± 2.6 (40)	5.48 ± 2.5 (63)	F2,152 = 1.187	p = 0.308	5.86 ± 2.7 (155)
CSS RRB	4.77 ± 2.8 (52)	4.63 ± 2.7 (40)	4.29 ± 2.9 (63)	F2,152 = 0.450	p = 0.638	4.54 ± 2.8 (155)
FSIQ	95.75 ± 18.9	105.06 ± 22.6	104.63 ± 17.8	F2,158 = 3.832	p = 0.024	101.82 ± 19.8	107.05 ± 16.5	F1,331 = 6.888	p = 0.009
ID	9	5	5	χ22 = 2.499	p = 0.287	19	11	χ21 = 2.965	p = 0.085
Mean CT (mm)	2.68 ± 0.1	2.71 ± 0.1	2.67 ± 0.1	F2,158 = 1.586	p = 0.208	2.69 ± 0.1	2.69 ± 0.1	F1,331 = 0.012	p = 0.912
Sex	25 F, 28 M	6 F, 36 M	19 F, 47 M	χ22 = 12.103	p = 0.002	50 F, 111 M	64 F, 108 M	χ21 = 1.399	p = 0.250
Time (yrs)	1.60 ± 0.3	1.60 ± 0.3	1.64 ± 0.2	F2,158 = 0.494	p = 0.611	1.62 ± 0.3	1.59 ± 0.3	F1,331 = 1.041	p = 0.308
Total SA (cm2)	2230.11 ± 271.08	2349.98 ± 159.96	2308.22 ± 228.0	F2,158 = 3.459	p = 0.034	2293.40 ± 232.0	2316.47 ± 225.0	F1,331 = 0.848	p = 0.358
T1 V Comm	81.60 ± 18.3	77.00 ± 12.5	73.74 ± 13.5	F2,158 = 4.031	p = 0.020	77.18 ± 15.3
T1 V Daily living	77.98 ± 18.7	76.90 ± 15.4	71.86 ± 12.4	F2,158 = 2.642	p = 0.074	75.19 ± 15.6
T1 V Social	73.38 ± 14.9	71.98 ± 11.2	70.55 ± 15.4	F2,158 = 0.582	p = 0.560	71.85 ± 14.2
T1 V Standard	75.60 ± 15.2	73.31 ± 10.1	69.50 ± 11.0	F2,158 = 3.717	p = 0.026	72.50 ± 12.5
∆ V Comm	−15.06 ± 13.1	−2.55 ± 6.8	9.15 ± 13.0	F2,158 = 62.752	p < 0.001	−1.87 ± 15.6
∆ V Daily living	−10.40 ± 8.5	0.14 ± 7.4	8.59 ± 8.7	F2,158 = 76.666	p < 0.001	0.14 ± 11.6
∆ V Social	−7.83 ± 9.9	2.45 ± 7.8	12.36 ± 10.1	F2,158 = 66.828	p < 0.001	3.13 ± 12.8
∆ V standard	−11.23 ± 8.0	0.05 ± 2.0	9.86 ± 5.5	F2,158 = 187.437	p < 0.001	0.36 ± 10.8
T2 V Comm	66.55 ± 22.1	74.45 ± 11.3	82.89 ± 15.1	F2,158 = 13.710	p < 0.001	75.31 ± 18.3
T2 V Daily living	67.58 ± 16.9	77.05 ± 16.8	80.45 ± 12.9	F2,158 = 10.668	p < 0.001	75.33 ± 16.3
T2 V Social	65.55 ± 19.9	74.43 ± 11.0	82.91 ± 13.7	F2,158 = 18.497	p < 0.001	74.98 ± 17.1
T2 V Standard	64.38 ± 18.7	73.36 ± 10.8	79.36 ± 11.0	F2,158 = 16.961	p < 0.001	72.86 ± 15.3

Data are expressed as mean ± standard deviation (n, unless as specified at the top of the column).

ADI autism diagnostic interview (comm: communication subscale, rrb restricted and repetitive behaviour subscale, social social subscale), CSS autism diagnostic observation schedule calibrated severity score (sa social affect subscale, rrb restricted and repetitive behaviour subscale, total overall score), CT cortical thickness, F female, FSIQ full-scale IQ, ID intellectual disability, M male, SA surface area, T1 measure at timepoint 1, T2 measure at timepoint 2, V Vineland Adaptive Behaviour Scale (comm communication domain, daily living daily living domain, social social domain, standard composite score), ∆ measurement of change between timepoint 1 and 2.

P values are not corrected for multiple comparisons.