Table 1.

Sample characteristics

Characteristics	High-staffing units (N=13,138)		Low-staffing units (N=11,540)		Standardized difference (%)
	n	%	n	%
Quartile of number of new psychiatric admissions (range)
First quartile (103–217)	1,874	14.3	4,197	36.4	−52.5
Second quartile (218–307)	2,480	18.9	3,689	32.0	−30.4
Third quartile (308–417)	4,355	33.1	1,893	16.4	39.4
Fourth quartile (418–1,082)	4,429	33.7	1,761	15.3	43.8
Age (years)
0–19	297	2.3	329	2.9	−3.8
20–39	3,425	26.1	2,528	21.9	9.8
40–64	5,411	41.2	4,320	37.4	7.8
65–74	1,862	14.2	1,739	15.1	−2.5
≥75	2,143	16.3	2,624	22.7	−16.2
Sex, women	7,345	55.9	6,459	56.0	−0.2
Charlson index
0	7,320	55.7	5,934	51.4	8.6
1	2,864	21.8	2,579	22.3	−1.2
2	1,373	10.5	1,334	11.6	−3.5
≥3	1,581	12.0	1,693	14.7	−7.9
History of psychiatric visit within 90 days	10,312	78.5	8,722	75.6	6.9
History of admission to ICU within 90 days	297	2.3	214	1.9	2.8
Voluntary admission	7,993	60.8	7,289	63.2	−4.9
Principal diagnosis (ICD-10 codes)
Schizophrenia (F2)	4,570	34.8	4,108	35.6	−1.7
Bipolar affective disorders (F30–F31)	1,415	10.8	1,068	9.3	5.0
Unipolar depressive disorders (F32–F33, F341)	2,743	20.9	2,045	17.7	8.1
Dementia (F00–F03, G30–G31)	974	7.4	1,364	11.8	−15.0
Other	3,436	26.2	2,955	25.6	1.4

Note: Patient-to-psychiatrist ratio of 16:1 (high-staffing units) vs 48:1 (low-staffing units).

Abbreviations: ICD, International Classification of Diseases; ICU, intensive care unit.