Table 5. Multiple logistic regression analysis of the association between feeling unhappy at school and each of the factors.

	Junior high school		Senior high school
	Unhappy at school		Unhappy at school
	AOR	95%CI	AOR	95%CI
Sex*
Boys	1.00		1.00
Girls	0.71	0.65–0.78	0.68	0.64– 0.72
Grade*
7 and 10	1.00		1.00
8 and 11	1.21	1.09–1.35	0.95	0.88–1.02
9 and 12	0.83	0.74–0.94	0.88	0.81–0.95
Intending to study at university*
Yes	1.00		1.00
No	0.98	0.86–1.11	1.36	1.27–1.45
Not yet decided	1.79	1.54–2.08	2.34	2.14–2.56
Participating in extracurricular activities*
Yes	1.00		1.00
No	1.77	1.59–1.97	1.87	1.75–1.99
Having breakfast*
Everyday	1.00		1.00
Sometimes	1.59	1.39–1.82	1.27	1.16–1.39
Seldom	2.27	1.93–2.67	1.94	1.77–2.13
Bedtimes*
Before or at midnight	1.00		1.00
After midnight	1.45	1.32–1.59	1.21	1.13–1.29
Smoking (past 30 days)*
No	1.00		1.00
Yes	2.35	1.90–2.90	1.6	1.43–1.79
Drinking (past 30 days)*
No	1.00		1.00
Yes	1.39	1.22–1.58	1.26	1.14–1.32
Mental health status*
Good	1.00		1.00
Poor	6.75	6.08–7.50	4.51	4.19–4.86

Abbreviations: AOR = adjusted odds ratio, CI = confidence interval.

Feeling unhappy at school: Students who selected “No, I don't” in response to the question asking whether the respondent felt happy at school (answer options: “Yes, I do”, “Yes and no”, and “No, I don't”).

Subjects for whom data were missing were excluded from the analysis.

Sex, Grade, Intending to study at university, Participating in extracurricular activities, Having breakfast, Bedtimes, Smoking, Drinking, and Mental health status were used as covariance values.

For calculation of the P values, a multivariate analysis model was used, *P<0.01.