Reference		Outcome	Tier a	Risk of bias domains b
Reference	Design	Outcome	Tier	Confidence in exposure (KEY)	Confidence in outcome (KEY)	Confounding (KEY) d	Appropriate comparison groups	Attrition	Other threats to internal validity
Cohort studies
Dion et al. (2018)	PC	IQ	1	+	+	+	+	−	+
Miyake et al. (2022)	PC	Behaviour	1	+	+	+	+	−	+
Rahman et al. (2017)	PC	IQ	1	+	++	+	+	+	+
	PC	Behaviour	1	+	++	+	+	+	+
Schullehner et al. (2020)	PC	ADHD	1	+	++	+	+	+	+
Rodrigues et al. (2016)	PC	Neurodevelopment	2	+	+	−	+	−	+
Cross‐sectional studies
Bouchard et al. (2011)	CS	IQ	1	+	++	+	+	+	+
Bouchard et al. (2018)	CS	IQ	1	+	++	+	+	+	+
Khan et al. (2011)	CS	Behaviour	1	+	+	+	+	+	+
Oulhote et al. (2014)	CS	Memory	1	+	+	+	+	+	+
	CS	Attention	1	+	+	+	+	+	+
	CS	Motor	1	+	+	+	+	+	+
	CS	Hyperactivity	1	+	+	+	+	+	+
Dion et al. (2016)	CS	MRI	2	+	++	−	+	+	+
Wasserman et al. (2004)	CS	IQ	1	+	+	+	+	+	+
Wasserman et al. (2006)	CS	IQ	1	+	+	+	+	+	+
Wasserman et al. (2011)	CS	IQ	1	+	++	+	+	+	+
Khan et al. (2012)	CS	Academic achievement	2	+	+	−	+	+	+
Kondakis et al. (1989)	CS	Neurological symptoms	2	−	+	−	+	+	+
Nascimento et al. (2016)	CS	Cognitive function	2	+	+	− c	+	+	+
Parvez et al. (2011)	CS	Motor function	2	+	++	−	+	+	+
Vieregge et al. (1995)	CS	Neurological symptoms	2	+	++	−	+	−	+
Nascimento et al. (2015)	CS	IQ	3	+	NR	−−	−	+	+

Abbreviations: ADHD, attention‐deficit hyperactivity disorder; CS, cross‐sectional; IQ, intelligence quotient; PC, prospective cohort.

^a The individual rating for each question was combined by an algorithm and translated to an overall tier of reliability for each individual study (RoB tier 1: low RoB; RoB tier 2: moderate RoB; RoB tier 3: high RoB).

^b Expert judgement was translated into a rating scale for each question to be answered as follows: (++): definitely low RoB; (+): probably low RoB; (NR): not reported; (−): probably high RoB; (− −): definitively high RoB.

^c Different from the preparatory work, the Panel identified cause for concern regarding the risk for confounding.

^d For pregnancy and children studies, the following factors were considered as key confounders: offspring age, offspring sex, maternal (or parental) socioeconomic status and/or education, prematurity (conditional), maternal smoking (conditional), maternal alcohol consumption (conditional), parity/number of siblings (conditional), other contaminants (conditional), birth weight (conditional); for pregnancy and children studies, the following factors were considered as key confounders: age at outcome assessment, sex, socioeconomic status and/or education, smoking, ethnicity (conditional), other contaminants (conditional).