Validity of single item responses to short message service texts to monitor depression: an mHealth sub-study of the UK ACUDep trial

Table 2 Summary of exploratory factor analysis item factor loadings^a of PHQ-9 and R-SMS-DS scores at 3 months follow-up

	Group 1			Group 2			Group 3
	N = 602 patients with PHQ-9			N = 337 patients with PHQ-9 & R-SMS-DS (any time)			N = 213 patients with PHQ-9 & R-SMS-DS (within 6 days)
	Loadings			Loadings			Loadings
	One-Factor	Affective	Somatic	One-Factor	Affective	Somatic	One-Factor	Affective	Somatic
PHQ-9 Item Descriptive/Variance explained	64 %	--- 73 % ---		61 %	--- 69 % ---		61 %	--- 70 % ---
1. Loss of interest (anhedonia)	.852	.632	-	.855	.540	-	.854	.448	.453
2. Depressed mood	.856	.875	-	.876	.768	-	.882	.683	-
3. Sleep disturbance	.778	-	.942	.761	-	.973	.740	-	.994
4. Fatigue	.794	-	1.078	.794	-	1.041	.779	-	.831
5. Appetite changes	.718	-	.640	.700	-	.617	.719	-	.573
6. Feeling bad about oneself	.816	.972	-	.840	1.244	-	.846	1.169	-
7. Concentration difficulties	.791	.554	-	.738	.411	-	.746	-	.634
8. Psychomotor disturbance	.735	.507	-	.690	.405	-	.700	-	.714
9. Thoughts of death or self-harm	.704	.894	-	.724	.860	-	.719	.826	-
R-SMS-DS: ‘How depressed have you felt?’	n/a^b	n/a^b	n/a^b	.656	.501	-	.692	.616	-
Correlation between factors		--- .834 ---			--- .820 ---			---.793 ---

^aLoadings < 0.400 suppressed
^bGroup 1 analyses excluded the SMS score, as this was not available for all patients