Table 3. Biochemical studies (metabolomics) available for meta-analysis.

Systems	Biomarkers	Biological fluids	Authors	Populations	Sample size		Results	Eligibility	Reasons
					ADHD (N)	CTRL (N)
Circadian rhythms	Cortisol	Saliva	Hirvikoski et al.46	Swedish	28	28	No	Excluded	No diagnosis available
			Lackschewitz et al.69	German	18	18	No	Included
			Baird et al.70	UK	13	19	Alterations	Included
			Raz et al.71	Israel	24	25	No	Included
PUFAs	AA	RBC	Young et al.72	Canada	36	35	No	Excluded	No enough studies
		Serum	Young et al.72	Canada	36	35	No	Included
			Laasonen et al.73	Finland	26	36	No	Included
			Irmish et al.74	Germany	15	15	Alterations	Included
	DHA	RBC	Young et al.72	Canada	36	35	Alterations	Excluded	No enough studies
		Serum	Young et al.72	Canada	36	35	Alterations	Included
			Laasonen et al.73	Finland	26	36	No	Included
			Irmish et al.74	Germany	15	15	Alterations	Included
	EPA	RBC	Young et al.72	Canada	36	35	No	Excluded	No enough studies
		Serum	Young et al.72	Canada	36	35	No	Included
			Laasonen et al.73	Finland	26	36	No	Included
			Irmish et al.74	Germany	15	15	Alterations	Included
	DyLA	RBC	Young et al.72	Canada	36	35	No	Excluded	No enough studies
		Serum	Young et al.72	Canada	36	35	No	Included
			Laasonen et al.73	Finland	26	36	No	Included
			Irmish et al.74	Germany	15	15	Alterations	Included

Abbreviations: AA, arachidonic acid; ADHD, attention-deficit hyperactivity disorder; DHA, docosahexaenoic acid; DyLA, dihomogammalinolenic acid; EPA, eicosapentaenoic acid; N, sample size; PUFAs, polyunsaturated fatty acids; RBC, red blood cells.

No indicates absence of alterations on levels of a biomarker.