Table 1.

Baseline demographic characteristics and clinical features of participants with treatment-resistant depression receiving TAU with or without adjunctive VNS + TAU (two-sided t-test P-value for continuous data and asymptotic normal test P-value for categorical data)

	VNS + TAU (N=328)		TAU (N=271)		P-value
	Mean or N	SD or %	Mean or N	SD or %
Age (years)	48.8	10.37	50.0	10.80	0.168
Number of female subjects	225	68.6	192	70.8	0.612
Number of white subjects	318	97.0	246	90.8	0.002
Age at initial onset of depression (years)	20.8	12.12	21.4	11.54	0.536
Age at initial diagnosis of depression (years)	29.0	10.90	29.7	11.67	0.451
Number of failed treatments for depression	8.0	3.04	7.4	2.93	0.014
Lifetime number of diagnosed depressive episode	15.1	24.34	11.7	24.56	0.090
Psychiatric hospitalizations within prior 5 years	2.8	4.63	1.5	2.87	<0.001
Lifetime suicide attempts	2.0	4.35	1.2	2.32	0.004
History of electroconvulsive therapy	191	58.2	107	39.5	<0.001
DSM-IV-TR primary diagnosis
Moderate recurrent major depression	40	12.2	66	24.4	<0.001
Severe recurrent major depression	133	40.5	85	31.4	0.025
Moderate single-episode major depression	12	3.7	29	10.7	0.001
Severe single-episode major depression	46	14.0	32	11.8	0.496
Bipolar I, currently moderately severe major depressive episode	19	5.8	18	6.6	0.795
Bipolar I, currently severe major depressive episode	46	14.0	10	3.7	<0.001
Bipolar II, currently depressed	32	9.8	31	11.4	0.592
Baseline scores
Montgomery–Åsberg Depression Rating Scale	33.2	7.67	29.5	6.40	<0.001
Clinical Global Impressions-Severity	5.2	0.78	4.7	0.72	<0.001
Quick Inventory of Depressive Symptomatology-Self Report	18.3	4.67	15.8	4.92	<0.001

Abbreviations: TAU, treatment as usual; VNS, vagus nerve stumulation.