TABLE 1.

Demographics and clinical characteristics of the participants at T1, T2, and T3

Characteristic	T1	T2	T3
	(n = 373)	(n = 154)	(n = 116)
Male sex, n (%)	258 (69.2%)	102 (66%)	92 (79.3%)
ADOS module completed, a n (%)
Module 1	315 (84.5%)	51 (33.1%)	31 (27.0%)
Module 2	58 (15.5%)	42 (27.3%)	12 (10.4%)
Module 3	–	61 (39.6%)	72 (62.6%)
ADOS‐2 calibrated severity score, a mean (SD)	7.5 (1.7)	7.0 (2.1)	7.6 (1.9)
Age (years) at IQ testing, mean (SD) [range]	3.0 (0.5)	5.6 (0.9)	11.5 (0.9)
	[1.7–5.0]	[4.3–9.4]	[9.0–13.6]
IQ b
Full scale, c , d mean (SD) [range]	62.7 (20.7)	79.1 (32.3)	78.8 (32.1)
	[20.5–132.5]	[17.9–133.0]	[24 – 170.0]
Verbal, d mean (SD) [range]	55.6 (25.0)	74.8 (33.0)	73.2 (36.0)
	[14.0–128.0]	[12.1–128.0]	[24 – 157.0]
Nonverbal, e mean (SD) [range]	69.9 (18.7)	82.2 (31.2)	82.4 (30.4)
	[25.5–137.0]	[22.3–140.0]	[24 – 170.0]
VABS communication, f mean (SD)	72.9 (15.7)	81.0 (19.7)	72.8 (18.3)
CBCL internalizing, g mean (SD)	62.2 (9.5)	59.4 (9.7)	60.0 (10.1)
CBCL externalizing, h mean (SD)	59.3 (10.9)	55.8 (10.3)	55.1 (9.5)

Abbreviations: ADOS‐2, Autism Diagnostic Observation Schedule; CBCL, Child Behavior Checklist; Second, Edition; VABS, Vineland Adaptive Behavioral Scales.

^a 1 participant ADOS was not completed at T3.

^b All participants had IQ assessed using MSEL at T1; at T2, 28 participants were assessed using MSEL and 126 using Differential Abilities Scales‐II (DAS‐II) (DAS); at T3, all participants were assessed using DAS.

^c 1 participant's IQ could not be assessed at T2.

^d 1 participant's IQ could not be assessed due to aggressive behavior at T3.

^e 2 participants' IQs could not be computed because nonverbal scores were out of range of the publisher's norms.

^f 31 participants at T1, 21 at T2, and 6 at T3 are missing this variable.

^g 49 participants at T1, 34 at T2, and 13 at T3 are missing this variable.

^h 43 participants at T1, 26 at T2, and 12 at T3 are missing this variable.