Table 4.

Spearman’s correlations for ADHD symptom scores and serum variables, adjusted for cotinine and age

		Trp	Kyn	KTR	HK	KA	XA	AA	HAA	QA	Vit. B2	Vit. B6
All
N = 248	ASRS total score	−0.15*	−0.14*	0.04	0.04	−0.08	0.01	0.04	−0.05	−0.04	−0.13*	−0.06
N = 250	ASRS inattentive	−0.15*	−0.13*	0.06	0.02	−0.08	−0.01	0.06	−0.03	−0.01	−0.06	−0.03
N = 251	ASRS hyperactive/impulsive	−0.14*	−0.16*	0.02	0.03	−0.09	0.01	0.02	−0.07	−0.07	−0.17*	−0.05
N = 243	WURS total score	−0.18*	−0.15*	0.03	−0.01	−0.14*	−0.08	0.05	−0.08	−0.05	−0.09	−0.01
ADHD
N = 121	ASRS total score	−0.20*	−0.16	0.07	0.11	−0.05	0.01	0.05	−0.01	−0.14	−0.17	−0.22*
N = 122	ASRS inattentive	−0.20*	−0.16	0.08	0.11	−0.03	0.06	0.02	0.07	−0.08	−0.09	−0.19*
N = 123	ASRS hyperactive/impulsive	−0.17	−0.14	0.03	0.09	−0.03	−0.02	0.06	−0.05	−0.12	−0.17	−0.14
N = 115	WURS total score	−0.27*	−0.13	0.13	−0.08	−0.18	−0.16	0.15	−0.09	−0.16	0.05	−0.04
Control
N = 127	ASRS total score	−0.05	−0.11	0.03	−0.11	−0.12	0.01	−0.05	−0.07	−0.10	−0.14	−0.04
N = 128	ASRS inattentive	0.01	−0.02	0.03	−0.13	−0.10	−0.04	0.02	−0.01	−0.01	−0.07	0.03
N = 128	ASRS hyperactive/impulsive	−0.10	−0.19*	−0.01	−0.09	−0.13	0.05	−0.12	−0.10	−0.17	−0.19*	−0.08
N = 128	WURS total score	−0.14	−0.14	0.03	−0.07	−0.11	−0.07	−0.07	−0.06	−0.08	−0.11	−0.01

The 18-item ASRS (Adult ADHD Self-report Scale) is used to assess current ADHD symptom burden, with nine questions specific to hyperactivity/impulsivity and nine questions specific to inattentiveness. WURS (Wender Utah Rating Scale) consists of 25 items for retrospective assessment of childhood ADHD symptom burden. Significance: <0.05 ‘*’

Trp tryptophan, Kyn kynurenine, KTR kynurenine/tryptophan ratio, HK 3-hydroxykynurenine, KA kynurenic acid, XA xanthurenic acid, AA anthranilic acid, HAA 3-hydroxyanthranilic acid, QA quinolinic acid, Cot cotinine