Table 2.

Intercorrelations and Descriptive Statistics of Study Variables

Variable	1	2	3	4	5	6	7	8	9	10	11	12	13	14
1. Sex	--	.01	.02	.01	.08**	.09**	.04	.07**	.07**	.05*	−.01	.01	.05*	.06*
2. Sleep quality		--	.41***	.42***	.21***	.32***	.18***	.28***	.69***	.50***	.32***	.21***	.24***	.21***
3. Sleep latency			--	.22***	.22***	.33***	.22***	.11***	.67***	.56***	.21***	.14***	.18***	.15***
4. Shorter sleep duration				--	.37***	.10***	.04	.21***	.60***	.45***	.21***	.17***	.17***	.16***
5. Sleep efficiency					--	.17***	.12***	.06**	.54***	.37***	.15***	.12***	.08***	.09***
6. Sleep disturbancea						--	.24***	.22***	.54***	.41***	.28***	.15***	.23***	.20***
7. Sleep medication							--	.11***	.48***	.31***	.11***	.04	.12***	.09***
8. Daytime sleepinessb								--	.41***	.29***	.28***	.17***	.21***	.19***
9. Total sleep problems									--	.75***	.42***	.28***	.33***	.29***
10. Sleep status										--	.30***	.19***	.24***	.22***
11. Depressive symptoms											--	.75***	.55***	.44***
12. Depression status												--	.42***	.32***
13. SBQ-R total score													--	.84***
14. Suicide risk status														--
Mean	--	1.20	1.43	0.94	0.54	1.28	0.44	1.14	6.95	--	0.57	--	5.17	--
SD	--	0.65	0.98	0.86	0.79	0.56	0.85	0.78	3.20	--	0.62	--	2.81	--

Note. N = 1,700. For sex, 0 = male, 1 = female (n = 1,692 for these correlations). For depression status, 0 = not severe depression score on Depression Anxiety Stress Scale (DASS), 1 = severe depression score on DASS. For sleep status, 0 = good sleep, 1 = poor sleep. For suicide risk, 0 = not at risk, 1 = at risk. SBQ-R = Suicidal Behavior Questionnaire-Revised.

^aFor intercorrelations of the individual PSQI Sleep Disturbance items with the depression and suicide variables, see Table S2

^bThe daytime sleepiness variable is the single “how often had you had trouble staying awake while driving, eating meals, or engaged in social activity?” PSQI item.

^*p < .05.

^**p < .01.

^***p < .001.