Table 1.

Principal component structure, variance accounted for (h²), factor variances for the IDS-SR30 and the IDS-C30 (23 domains scored)

Domain	IDS-SR30			IDS-C30
	I	II	h2	I	II	h2
Sleep	0.50	0.11	0.26	0.54	0.18	0.32
Sad mood	0.82	−0.09	0.68	0.82	−0.11	0.68
Irritability	0.68	0.08	0.47	0.62	0.06	0.39
Anxiety/Tension	0.75	0.17	0.60	0.70	0.21	0.54
Mood reactivity	0.68	−0.32	0.56	0.70	−0.31	0.59
Diurnal variation	0.24	0.13	0.08	0.31	0.32	0.20
Distinct quality to mood	0.51	−0.27	0.33	0.30	−0.17	0.12
Appetite/Weight	0.45	−0.03	0.20	0.41	0.02	0.17
Concentration/Decision making	0.72	0.01	0.53	0.64	−0.03	0.41
Self view	0.69	−0.22	0.53	0.71	−0.17	0.53
Future view	0.72	−0.30	0.60	0.72	−0.28	0.60
Thoughts of death and suicide	0.57	−0.11	0.34	0.61	−0.19	0.40
General interest	0.74	−0.30	0.64	0.76	−0.27	0.65
Energy level	0.74	−0.11	0.56	0.72	0.00	0.52
Capacity for pleasurea	0.76	−0.35	0.70	0.68	−0.41	0.63
Interest in sex	0.52	−0.30	0.36	0.54	−0.20	0.33
Restlessness/Agitation	0.63	0.20	0.43	0.58	0.21	0.38
Somatic complaintsb	0.53	0.42	0.46	0.46	0.51	0.47
Sympathetic arousalb	0.59	0.56	0.66	0.57	0.48	0.56
Panic/Phobia	0.59	0.36	0.47	0.54	0.17	0.32
Gastrointestinal complaintsb	0.35	0.43	0.31	0.32	0.46	0.31
Interpersonal sensitivity	0.62	0.16	0.41	0.54	−0.07	0.30
Leaden paralysis	0.64	0.29	0.49	0.57	0.31	0.42
Factor variance	0.39	0.07	0.46	0.36	0.07	0.43

^aThe presence of the capacity for pleasure also contributes to the second component for only the IDS-C₃₀.

^bThese three items contribute to the second principal component for both the IDS-C₃₀ and the IDS-SR₃₀.

Note: Since the results were obtained from the principal components, the variances accounted for in each item (h²) are the sum of squared structure elements, eg, 0.50² + 0.11² = 0.26 for domain 1 on the IDS-C₃₀.