Cognitive impairment and pain in depression: The mediating role of the kynurenine pathway

Table 1 Demographic and clinical characteristics in the with- and without painful physical symptoms groups, n (%)

Variable	With PPS group (n = 33)	Without PPS group (n = 37)	t/z/χ2 value	P value
Sex (female/male)	16/17	23/14	1.322	0.250
Age (years)	32.61 ± 13.15	32.35 ± 13.02	-0.312	0.755
Body mass index (kg/m2)	23.99 ± 2.97	23.41 ± 4.30	-1.553	0.120
Education (years)	13.67 ± 3.28	14.27 ± 3.07	-0.756	0.450
Age of onset	27.21 ± 12.23	28.35 ± 13.60	-0.053	0.958
Hamilton Depression Scale	23.56 ± 7.42	19.54 ± 6.02	-2.052	0.040
Hamilton Anxiety Scale	20.52 ± 9.37	14.30 ± 6.72	-3.156	0.002
Short-form of McGill pain questionnaire	18.00 ± 12.56	N/A
Visual analog scale	4.85 ± 1.79	N/A
Medication			0.165	0.983
Selective serotonin reuptake inhibitors	20 (60)	23 (62)
Serotonin norepinephrine reuptake inhibitors	9 (27)	9 (24)
Other antidepressants	6 (18)	8 (22)
Antipsychotics	3 (9)	3 (8)
Mood stabilizers	15 (45)	18 (49)

N/A: Not applicable; PPS: Painful physical symptoms.

Table 2 Differences in cognition between the with and without painful physical symptoms groups

Variable	With PPS group (n = 33)	Without PPS group (n = 37)	F value	P value
Verbal learning	53.70 ± 7.79	53.70 ± 9.60	0.069	0.794
Reasoning and problem solving	49.88 ± 9.92	52.70 ± 9.81	1.707	0.196
Visual learning	46.97 ± 9.52	50.00 ± 10.31	1.383	0.244
Social cognition	44.61 ± 13.34	45.38 ± 12.08	0.076	0.784
Attention/vigilance	48.85 ± 10.34	52.92 ± 5.93	4.029	0.049
Speed of processing working memory	51.00 ± 9.32	55.46 ± 8.39	3.987	0.050
Total MATRICS consensus	52.52 ± 9.38	56.03 ± 7.58	2.350	0.130
Cognitive battery	48.33 ± 8.93	53.16 ± 6.45	4.107	0.047

PPS: Painful physical symptoms.

Table 3 Differences in tryptophan-kynurenine pathway metabolites between the with and without painful physical symptoms groups

Variable	With PPS group (n = 33)	Without PPS group (n = 37)	F value	P value
TRP	11.18 ± 2.17	11.51 ± 1.82	1.657	0.202
KYN	396.58 ± 92.55	333.62 ± 92.46	6.508	0.013
KA	2.52 ± 0.92	2.70 ± 2.12	1.063	0.306
QA	29.61 ± 13.12	27.25 ± 15.70	0.153	0.697
3-hydroxykynurenine	4.35 ± 1.75	4.13 ± 2.14	0.494	0.485
5-hydroxytryptamine	33.39 ± 40.01	22.71 ± 27.91	1.560	0.216
TRP-KYN	35.99 ± 7.82	29.00 ± 7.15	14.076	< 0.001
KA/QA	0.09 ± 0.04	0.10 ± 0.05	1.132	0.291

KA: Kynurenic acid; KYN: Kynurenine; PPS: Painful physical symptoms; QA: Quinolinic acid; TRP: Tryptophan.