Table 2.

Subgroup meta-analysis and analysis of heterogeneity

Subgroup	No. of studies	No. of subjects	OR (95%CI)	Heterogeneity		P value
				I2(%)	P value
Year of publication
1997 ~  2010	10	166,949	2.53 (1.75 3.66)	76.8	<  0.001	<  0.001
2010 ~  2019	8	31,944	2.10 (0.80 5.53)	99.5	<  0.001	0.134
Study design
Retrospective	6	171,176	1.79 (1.33 2.42)	83.1	<  0.001	<  0.001
Prospective	6	4856	2.25 (1.39 3.64)	75.3	0.001	0.001
Cross-sectional	6	22,861	2.45 (0.79 7.61)	98.9	<  0.001	0.122
Sample size
< 1000	11	2234	2.99 (1.28 6.98)	99.2	<  0.001	0.011
> 1000	7	196,659	1.50 (1.24 1.81)	53.8	0.043	<  0.001
Age of subjects
Mean < 40	12	189,712	2.75 (1.26 6.03)	99.4	<  0.001	0.011
Mean > 40	6	9181	1.81 (1.30 2.51)	73.4	0.002	<  0.001
Diagnostic criteria
ICD-10	2	1541	2.13 (1.10 4.12)	43.2	0.185	0.025
DSM-III-R	4	2681	4.80 (2.90 7.67)	0	0.720	<  0.001
DSM-IV	11	174,541	2.11 (0.96 4.65)	99.4	<  0.001	0.063
CES-D	1	20,130	1.12 (0.92 1.37)	–	–	0.265
Diagnostic outcome
Major depression	12	5336	2.92(1.42 5.98)	97.5	<  0.001	0.003
Depression	6	193,557	1.41(1.14 1.73)	75.6	0.001	0.001
Sleep disorder type
Insomnia	12	172,759	2.29 (1.69 3.10)	86.1	<  0.001	<  0.001
Nightmares	3	582	4.47 (2.00 9.97)	0	0.490	<  0.001
Hypersomnia	3	2914	2.19 (0.77 6.21)	93.0	<  0.001	0.140
Other	7	27,144	2.41 (0.80 7.24)	99.6	<  0.001	0.117
Suicidal behavior type
Suicidal ideation	13	194,419	2.32 (1.11 4.88)	99.2	<  0.001	0.026
Suicide attempts	7	193,834	2.41 (1.45 4.02)	87.7	<  0.001	0.001
Completed suicide	2	163,668	1.24 (1.00 1.53)	0	0.445	0.050
Other	2	225	4.19 (2.82 6.21)	0	0.654	<  0.001

OR Odds ratio, ICD-10 International classification of diseases, tenth revision, DSM The diagnostic and statistical manual of mental disorders, CES-D Center for epidemiology scale for depression