Linkage of kynurenine pathway metabolites to neuroinflammation in drug-naive children with attention-deficit/hyperactivity disorder: A cross-sectional, case–control study

doi:10.5409/wjcp.v15.i2.115284

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Jun 9, 2026 (publication date) through May 16, 2026

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World Journal of Clinical Pediatrics

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2219-2808

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Copyright: ©Author(s) 2026. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial (CC BY-NC 4.0) license. No commercial re-use. See permissions. Published by Baishideng Publishing Group Inc.

World J Clin Pediatr. Jun 9, 2026; 15(2): 115284
Published online Jun 9, 2026. doi: 10.5409/wjcp.v15.i2.115284

Table 1 Socio-demographic, clinical characteristics, and Conner Parent Rating Scale-48 subscale scores of children with attention-deficit/hyperactivity disorder and control, n (%)/median (interquartile range)

	ADHD group (n = 51)	Control group (n = 36)	P value
Males/females	34/17 (67/33)	17/19 (47/53)	0.070
Smoking (yes)	5 (9.8)	-	0.074
Psychiatric illness in the family	22 (43.1)	8 (22.2)	0.043
Age (months)	151 (115-169)	154 (123-180)	0.438
BMI percentile	52 (24.8-74.5)	66.4 (27.9-75.4)	0.957
Time since symptoms onset (months)	36 (24-60)	-	-
CPRS-48 subscale scores
Conduct problems	10 (5-16)	2 (0-3)	< 0.001
Learning problems	7 (6-10)	1 (0-3)	< 0.001
Psychosomatic	6 (2-9)	0.5 (0-3.5)	< 0.001
Impulsive-hyperactive	7 (5-9)	2.5 (1-5)	< 0.001
Anxiety	8 (5-12)	4 (2-6)	< 0.001
Total score	49 (32-69)	42 (7-24.5)	< 0.001

BMI: Body mass index; CPRS-48: Conner Parent Rating Scale-48.

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Table 2 Serum kynurenine pathway metabolite levels and associated ratios in attention-deficit/hyperactivity disorder and control group, median (interquartile range)

	ADHD group (n = 51)	Control group (n = 36)	P value
TRP (μmol/L)	174 (94-276)	210 (59-259)	0.914
KYN (nmol/L)	65.6 (54-77)	61.6 (48-81)	0.543
KYNA (nmol/L)	25.8 (21-36)	31.3 (27-39)	0.023
QUIN (μmol/L)	12.7 (10-16)	12 (10-15)	0.721
KYN/TRP × 1000 (IDO/TDO activity)	40 (40-82)	34.7 (20-94)	0.816
KYNA/KYN × 100 (KAT activity)	39 (32-61)	56.5 (36-75)	0.083
KYNA/QUIN (neuroprotective index)	2.3 (2.0-2.7)	2.5 (2.3-3.1)	0.025
QUIN/KYNA (neurotoxic index)	0.44 (0.37-0.50)	0.40 (0.32-0.44)	0.029
QUIN/KYN (KMO activity)	0.19 (0.13-0.28)	0.20 (0.14-0.28)	0.756

ADHD: Attention-deficit/hyperactivity disorder; KYN: Kynurenine; TRP: Tryptophan; IDO/TDO: Indoleamine 2,3-dioxygenase/tryptophan 2,3-dioxygenase; KYNA: Kynurenic acid; KAT: Kynurenine aminotransferases; QUIN: Quinolinic acid; KMO: Kynurenine monooxygenase.

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Table 3 Correlation between biochemical parameters and Conner Parent Rating Scale-48 subscale scores in the associated ratios in attention-deficit/hyperactivity disorder group

n = 51	CPRS-48, CP		CPRS-48, LP		CPRS-48, P		CPRS-48, I-H		CPRS-48, A		CPRS-48, total score
	r	P value	r	P value	r	P value	r	P value	r	P value	r	P value
TRP (μmol/L)	-0.237	0.093	-0.061	0.672	0.127	0.376	-0.001	0.994	-0.070	0.628	-0.083	0.564
KYN (nmol/L)	-0.152	0.286	0.006	0.964	0.096	0.501	-0.100	0.485	-0.158	0.270	-0.151	0.289
KYNA (nmol/L)	0.016	0.911	0.046	0.747	0.184	0.196	0.146	0.307	0.001	0.993	0.062	0.668
QUIN acid (μmol/L)	0.007	0.963	-0.075	0.602	0.076	0.594	0.063	0.663	-0.024	0.869	-0.005	0.970
KYN/TRP × 1000 (IDO/TDO)	0.165	0.248	0.054	0.708	-0.090	0.529	-0.059	0.680	0.039	0.788	0.032	0.824
KYNA/KYN × 100 (KAT activity)	-0.165	0.248	0.099	0.490	0.165	0.247	0.210	0.138	0.096	0.501	0.183	0.199
KYNA/QUIN (neuroprotective)	0.055	0.703	0.237	0.094	0.265	0.060	0.173	0.224	0.126	0.379	0.166	0.243
QUIN/KYNA (neurotoxic)	-0.058	0.685	-0.237	0.095	-0.264	0.061	-0.176	0.216	-0.127	0.373	-0.167	0.240
QUIN/KYN (KMO activity)	0.090	0.530	-0.032	0.824	0.050	0.728	0.151	0.291	0.050	0.726	0.101	0.479

Spearman correlational analysis was performed. r: Correlation coefficient. CPRS-48: Conner Parent Rating Scale-48; CP: Conduct problems; LP: Learning problems; P: Psychosomatic; I-H: Impulsive-Hyperactive; A: Anxiety; KYN: Kynurenine; TRP: Tryptophan; IDO/TDO: Indoleamine 2,3-dioxygenase/tryptophan 2,3-dioxygenase; KYNA: Kynurenic acid; KAT: Kynurenine aminotransferases; QUIN: Quinolinic acid; KMO: Kynurenine monooxygenase.

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Table 4 Correlation between biochemical parameters and time since symptoms onset, Conner Parent Rating Scale-48 subscale scores, Conner Parent Rating Scale-48 total score in the attention-deficit/hyperactivity disorder group

n = 51	Time since symptoms onset		CPRS-48, CP¹		CPRS-48, LP¹		CPRS-48, P¹		CPRS-48, I-H¹		CPRS-48, A¹		CPRS-48, total score¹
	r	P value	r	P value	r	P value	r	P value	r	P value	r	P value	r	P value
TRP (μmol/L)	0.032	0.825	-0.237	0.093	-0.061	0.672	0.127	0.376	-0.001	0.994	-0.070	0.628	-0.083	0.564
KYN (nmol/L)	0.082	0.565	-0.152	0.286	0.006	0.964	0.096	0.501	-0.100	0.485	-0.158	0.270	-0.151	0.289
KYNA (nmol/L)	0.050	0.728	0.016	0.911	0.046	0.747	0.184	0.196	0.146	0.307	0.001	0.993	0.062	0.668
QUIN (μmol/L)	0.162	0.256	0.007	0.963	-0.075	0.602	0.076	0.594	0.063	0.663	-0.024	0.869	-0.005	0.970
KYN/TRP × 1000 (IDO/TDO)	-0.040	0.783	0.165	0.248	0.054	0.708	-0.090	0.529	-0.059	0.680	0.039	0.788	0.032	0.824
KYNA/KYN × 100 (KAT activity)	0.107	0.455	-0.165	0.248	0.099	0.490	0.165	0.247	0.210	0.138	0.096	0.501	0.183	0.199
KYNA/QUIN (neuroprotective)	-0.105	0.463	0.055	0.703	0.237	0.094	0.265	0.060	0.173	0.224	0.126	0.379	0.166	0.243
OUIN/KYNA (neurotoxic)	0.117	0.413	-0.058	0.685	-0.237	0.095	-0.264	0.061	-0.176	0.216	-0.127	0.373	-0.167	0.240
OUIN/KYN (KMO activity)	0.195	0.170	0.090	0.530	-0.032	0.824	0.050	0.728	0.151	0.291	0.050	0.726	0.101	0.479

¹Spearman correlational analysis was performed.

r: Correlation coefficient; CPRS-48: Conner Parent Rating Scale-48; CP: Conduct problems; LP: Learning problems; P: Psychosomatic; I-H: Impulsive-Hyperactive; A: Anxiety; KYN: Kynurenine; TRP: Tryptophan; IDO/TDO: Indoleamine 2,3-dioxygenase/tryptophan 2,3-dioxygenase; KYNA: Kynurenic acid; KAT: Kynurenine aminotransferases; QUIN: Quinolinic acid; KMO: Kynurenine monooxygenase.

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Citation: Ünal K, Taş Torun Y, Erol ME, Özbaş C, Kurt ZK. Linkage of kynurenine pathway metabolites to neuroinflammation in drug-naive children with attention-deficit/hyperactivity disorder: A cross-sectional, case–control study. World J Clin Pediatr 2026; 15(2): 115284
URL: https://www.wjgnet.com/2219-2808/full/v15/i2/115284.htm
DOI: https://dx.doi.org/10.5409/wjcp.v15.i2.115284

Ünal K, Taş Torun Y, Erol ME, Özbaş C, Kurt ZK. Linkage of kynurenine pathway metabolites to neuroinflammation in drug-naive children with attention-deficit/hyperactivity disorder: A cross-sectional, case–control study. World J Clin Pediatr 2026; 15(2): 115284 [DOI: 10.5409/wjcp.v15.i2.115284]

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