Multi-regression analysis revealed a relationship between l-serine and methionine, a component of one-carbon metabolism, in the normal control but not in the schizophrenia

Table 3 Relationship between methionine and other factors in patients with schizophrenia and normal controls: multiple regression analysis

	Forced entry model			Backward elimination model
	β ± SD	p value	VIF	β ± SD	p value	VIF
Normal control
Sex	−0.33 ± 0.23	0.17	1.90	−0.33 ± 0.15	0.04	1.18
Age	0.55 ± 0.20	0.01	1.51	0.53 ± 0.15	<0.001	1.09
Smoking status	−0.05 ± 0.21	0.92	1.55
Vitamin B12	−0.11 ± 0.28	0.70	2.76
Folate	−0.08 ± 0.24	0.75	2.06
Homocysteine	−0.08 ± 0.21	0.71	1.55
l-serine	0.40 ± 0.28	0.17	2.79	0.43 ± 0.15	0.008	1.13
d-serine	−0.03 ± 0.29	0.92	3.06
Glycine	0.02 ± 0.28	0.94	1.91
Genotype131	−0.03 ± 0.19	0.89	1.25
Genotype133	0.08 ± 0.25	0.75	2.37
Patients with schizophrenia
Sex	−0.06 ± 0.28	0.83	2.71
Age	0.21 ± 0.37	0.57	4.76
Duration of illness	−0.02 ± 0.32	0.95	3.32
Smoking status	0.12 ± 0.25	0.63	2.19
CP equivalent dose	−0.01 ± 0.28	0.95	1.53
Vitamin B12	0.06 ± 0.22	0.74	1.29
Folate	−0.11 ± 0.21	0.61	1.64
Homocysteine	−0.29 ± 0.23	0.23	1.93	−0.35 ± 0.16	0.14	1.18
l-serine	0.15 ± 0.26	0.55	2.31
d-serine	−0.13 ± 0.27	0.63	2.58
Glycine	0.10 ± 0.26	0.67	2.05
Genotype131	0.32 ± 0.24	0.20	2.07	0.35 ± 0.16	0.14	1.36
Genotype133	0.21 ± 0.28	0.46	2.77	0.27 ± 0.18	0.14	1.18

β standardised partial regression coefficient, VIF variance inflation factor, CP chlorpromazine, SD standard deviation

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