. Author manuscript; available in PMC: 2026 Mar 31.

Published in final edited form as: J Affect Disord. 2026 Feb 23;405:121496. doi: 10.1016/j.jad.2026.121496

Table 2.

Confirmatory Factor Analysis (CFA) standardized item loadings and Item Response Theory (IRT) discrimination parameters of Patient Health Questionnaire (PHQ-8) in U.S. adults, grouped by chronic pain status.

CFA Standardized Item Loadings
		anhedonia	sadness	sleep	fatigue	appetite	self-blame	concentration	psychomotor
	n	λ₁	λ₂	λ₃	λ₄	λ₅	λ₆	λ₇	λ₈
NoCP	23,925	0.841	0.875	0.714	0.755	0.744	0.839	0.783	0.759
CP	7,063	0.833	0.876	0.755	0.731	0.731	0.834	0.777	0.727
HICP	2,611	0.812	0.884	0.665	0.734	0.685	0.823	0.754	0.690
IRT Discrimination Parameters
		anhedonia	sadness	sleep	fatigue	appetite	self-blame	concentration	psychomotor
	n	α₁	α₂	α₃	α₄	α₅	α₆	α₇	α₈
NoCP	23,925	2.821	3.167	1.810	2.085	2.109	2.978	2.389	2.290
CP	7,063	2.710	3.144	1.528	1.931	1.883	2.829	2.244	1.951
HICP	2,611	2.523	3.277	1.442	1.737	1.615	2.724	2.044	1.712

Abbreviations: NoCP= without chronic pain, CP= chronic pain, HICP = high-impact chronic pain.

Data Source: National Center for Health Statistics, National Health Interview Survey, 2019

Standardized item loadings: > 0.7 = “excellent” item performance; ≤ 0.7 and > 0.5 = “good” item performance.

Discrimination parameters: ≥ 1.70 = “quite satisfactory” discriminative ability; < 1.70 and ≥ to 1.35 = “good” discriminative ability.