Table 2 Familial correlations of the biochemical traits in the studied cohort.

Data	Group	Parent-offspring correlation (P-O)		Sibling-sibling correlation (S-S)				Father-mother correlation (F-M)
Data	Group	N pairs	Correlation (SE)	P-value	N pairs	Correlation (SE)	P-value	*N pairs	Correlation (SE)	P-value
Serotonin	^bAll	606	0.15 (0.043)	0.0005	187	0.13 (0.080)	0.11	165	0.058 (0.078)	0.46
	^aASD	382	0.12 (0.054)	0.029	30	0.094 (0.21)	0.66	162	0.066 (0.079)	0.41
	^aUnaffected	216	0.20 (0.070)	0.0063	35	0.18 (0.32)	0.59	84	0.094 (0.11)	0.40
AANAT	^bAll	460	0.23 (0.057)	0.0001	138	0.26 (0.11)	0.022	133	0.34 (0.077)	0.0001
	^bASD	314	0.22 (0.064)	0.0007	25	0.19 (0.21)	0.38	133	0.34 (0.077)	<0.0001
	^cUnaffected	140	0.36 (0.094)	0.0006	26	0.099 (0.22)	0.65	54	0.59 (0.091)	<0.0001
NAS	^aAll	328	0.38 (0.056)	<0.0001	101	0.21 (0.12)	0.11	96	0.13 (0.10)	0.20
	^aASD	214	0.40 (0.063)	<0.0001	12	0.42 (0.25)	0.13	95	0.16 (0.10)	0.13
	^cUnaffected	102	0.32 (0.11)	0.0077	20	0.63 (0.20)	0.014	38	0.080 (0.17)	0.64
ASMT	^aAll	354	0.28 (0.053)	<0.0001	104	0.23 (0.12)	0.071	107	−0.089 (0.097)	0.37
	^aASD	240	0.24 (0.061)	0.0001	13	0.59 (0.19)	0.013	107	−0.082 (0.097)	0.4019
	^aUnaffected	108	0.32 (0.090)	0.0012	21	0.51 (0.23)	0.058	40	−0.21 (0.16)	0.20
Melatonin	^aAll	518	0.13 (0.057)	0.027	173	0.27 (0.088)	0.0035	136	0.30 (0.078)	0.0003
	^bASD	318	0.055 (0.072)	0.45	28	0.23 (0.21)	0.29	132	0.31 (0.079)	0.0003
	^aUnaffected	192	0.21 (0.090)	0.025	35	0.62 (0.16)	0.0023	73	0.20 (0.11)	0.10

Significant p-values after Bonferroni correction are indicated in bold: 45 tests were performed, p-values < 1.11 × 10⁻³ (0.05/45) were considered as significant. N pairs, number of relative pairs included in the analysis; SE, Standard Error; ^aage was included in the model as a covariate; ^bage and sex were included in the model as covariates; ^cno covariates were included in the model. *Number of father-mother pairs (F-M): parents included in the analyses using all family members and in stratified analyses as described in Supplementary Table S4.

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