Is Earlier Better? The Relationship between Age When Starting Early Intervention and Outcomes for Children with Autism Spectrum Disorder: A Selective Review

Table 1

Methods features of studies reviewed.

Study	Research design	Sample size	Age (percent)			Follow-up	Variables and measurements
			<3 yrs	3-4 yrs	>4 yrs	Period	Cognitive	Adaptive	ASD severity	Language	Social
Studies with primarily preschoolers and older
Perry et al., 2011^1	Intervention, pre-post	332	6.7	24	70	M = 18.4 months	DQs derived from different tests	VABS	CARS	N/A	N/A
Kasari et al., 2012^2	Intervention, RCT 2 tx and 1 control group	40	15.9	68.2	15.9	5 years	DAS; SPA	N/A	ADOS	EVT	ESCS; PCX
Smith, Klorman, & Mruzek, 2015^3	Intervention, pre-post	71	30.9	53.2	13.6	12 and 24 months	MSEL	VABS	ADOS; ADI-R	MCDI; ESCS	WSQ
Eapen, Crncec, & Walter, 2016	Intervention, pre-post	49	0.6	30.3	62.4	M = 9.8 months	MSEL	VABS	ADOS; SCQ	N/A	N/A
Studies spanning age groups
Flanagan, Perry, & Freeman, 2012^1	Intervention, waitlist/TAU control	142	30.9	38.2	28	M = 22.4 months	MSEL; WPPSI	VABS	CARS	N/A	N/A
Pellicano, 2012^4	Longitudinal	37	40	37	23	Approx. 5 years M = 21.9 months	LIPS	N/A	ADI, ADOS-G, SCQ	PPVT-III	N/A
Virues-Ortega, Rodriguez, & Yu, 2013^3	Intervention, pre-post and trajectory analysis	24	30.9	30	39.1	Approx. 2 years	E-LAP; LAP-D	E-LAP; LAP-D	N/A	E-LAP; LAP-D	E-LAP; LAP-D
Hedvall 2015^1	Intervention, pre-post, two extreme groups	198	50	44	6	Approx. 2 years	DQs derived from different tests	VABS-II	BED, ABC	MCDI	VABS-II
Vivanti et al.,^3 2016	Intervention, pre-post	60	36.7	61.7	1.7	12 months	MSEL	VABS	ADOS-2	N/A	N/A
Studies with infants and toddlers
Itzchak & Zachor 2011^3	Intervention, two tx groups	78	100			12 months	MSEL	VABS	ADOS	MSEL VQ	N/A
Rogers et al., 2012^1	Intervention, RCT	98	100			12 weeks	MSEL	VABS	ADOS-T	MCDI	Tasks
Anderson, Liang, & Lord, 2013^4	Longitudinal	85	100			17 years	MSEL; DAS	VABS	ADOS; ADI-R	N/A	N/A
Tiura, Kim, Detmers, & Baldi, 2017^3	Intervention, pre-post and trajectory analysis	35	78	12		3 to 6 years	DP-3	DP-3	High vs. low severity based on clinician’s judgment	DP-3	DP-3
Vivanti et al., 2018^3	Intervention, RCT, two tx groups	44	100			9 months	MSEL; imitation task	VABS	SCQ RBS = R	LENA	M-COSMIC

¹Prediction study conducted after original intervention study was published. ²Prediction study conducted after additional follow-up period. ³Prediction analyses conducted concurrently with treatment effectiveness and presented in one publication. ⁴Longitudinal study; RCT = randomized controlled trial; TAU = treatment as usual; tx = treatment; DAS = Differential Ability Scales; SPA = Structured Play Assessment; MSEL = Mullen Scales of Early Learning; WPPSI = Wechsler Preschool and Primary Scale of Intelligence; LIPS = Leiter International Performance Scale; ADOS = Autism Diagnostic Observation Schedule; ADI-R = Autism Diagnostic Interview-Revised; VABS = Vineland Adaptive Behavior Scale; PPVT-III = Peabody Picture Vocabulary Test, 3^rd Edition; E-LAP = The Early Learning Accomplishment Profile; LAP-D = The Learning Accomplishment Profile-Diagnostic; BED = Best Estimate Diagnosis; ABC = Autism Behavior Checklist; CARS = Childhood Autism Rating Scale; SCQ = Social Communication Questionnaire; EVT = Expressive Vocabulary Test; MCDI = MacArthur–Bates Communicative Development Inventory; ESCS = Early Social Communication Scales; PCX = Parent-Child Interaction; WSQ = Wing Subtypes Questionnaire; DP-3 = Developmental Profile-3; RBS-R = Repetitive Behavior Scale-Revised; LENA = Language ENvironment Analysis; M-COSMIC = Modified Classroom Observation Schedule to Measure Intentional Communication.