Table 2.

Characteristics of the included latent class analysis studies.

References	Sampling frame	Analysis	Sample age	IQ	Questionnaires used	Classes
van der Meer et al. (64) Journal IF: 8.829*	General population and clinical sample (ASD, ADHD, or ASD + ADHD) (SPIDER, BOA) Netherlands n = 644	LCA	5-17 yrs	At least 70	ASD: 3 SCQ subscales ADHD: 5 CPRS-R:L subscale scores	1: “Normal” class (9.0 %) 2: “Normal” class (9.2 %) 3: “ADHD” class (16.9%) 4: “ADHD(+ASD)” class (23.2 %) 5: “ASD(+ADHD)” class (41.6 %)
Van der Meer et al. (65) Journal IF: 3.256*	General population (SPIDER) Netherlands n = 378	LCA	6-13 yrs M:F 1:1	At least 70	ASD: 5 AQ subscales ADHD: 2 SWAN subscales	1: Low ASD, Low ADHD (10.1%) 2: Medium ASD, Medium ADHD (54.2%) 3: High ASD, High ADHD (13.2%) 4: ADHD > ASD (18.3%) 5: ASD > ADHD (4.2%)
St. Pourcain et al. (66) Journal IF: 8.829*	General Population (AVON) England N = 5,383	LCGA	4-17 yrs	At least 70	ASD: 12 SCD items ADHD: 5 SDQ items	ASD: 1. Persistently Impaired: 10% 2. Low-risk: 90 % ADHD 1. Persistently Impaired: 3.94% 2. Intermediate risk: 8.07% 3. Childhood-Limited (5.25%) 4. Low-risk (82.74%)

AQ, Autism Quotient; AVON, Avon Longitudinal Study of Parents and Children; BOA, Biological Origins of Autism; CPRS-R:L, Connors Parent Rating Scale Revised Long; IF, Impact Factor; LCA, Latent Class Analysis; LCGA, Latent Class Growth Analysis; SCD, Social Communication Disorder Questionnaire; SDQ, Strengths and Difficulties Questionnaire; SCQ, Social Communication Questionnaire; SPIDER, Schoolkids Project Interrrelating DNA and Endophenotype Research; SWAN, Strengths and Weakness of ADHD Symptoms and Normal Behaviour Rating Scale; yr(s), year(s).

^*The journal impact factor is based off 2020 metrics (48).