Table 5.

Associations between gender, school grade, age at initial weekly Internet use, ownership of private portable phone, family rules regarding Internet use, and the risks of problematic Internet use (PIU: YDQ^a) score ≥ 5 points

	Total			Males			Females
	Adjusted OR	95% CI	p-value	Adjusted OR	95% CI	P-value	Adjusted OR	95% CI	P-value
Gender
Male	Reference
Female	1.656	1.175–2.334	0.004
School Grade
7th	Reference			Reference			Reference
8th	1.748	1.145–2.669	0.01	1.805	0.918–3.549	0.087	1.769	1.024–3.058	0.041
9th	1.980	1.285–3.052	0.002	2.107	1.067–4.161	0.032	1.959	1.114–3.447	0.020
Age at initial weekly Internet use
12≤	Reference			Reference			Reference
10–11	1.857	1.064–3.242	0.03	1.757	0.608–5.079	0.298	1.943	1.004–3.760	0.048
8–9	2.596	1.467–4.595	0.001	3.913	1.412–10.847	0.009	2.058	1.014–4.177	0.046
6–7	3.633	1.977–6.674	<0.001	4.481	1.488–13.497	0.008	3.328	1.589–6.969	0.001
≤5	7.422	3.691–14.923	<0.001	14.955	5.053–44.260	<0.001	2.977	0.975–9.087	0.055
Smartphone ownership
None	Reference			Reference			Reference
Smartphone	4.083	1.771–9.416	0.001	1.859	0.644–5.365	0.251	8.535	2.076–35.625	0.003
Family rules regarding Internet use
No	Reference			Reference			Reference
Yes	0.746	0.671–1.331	0.945	0.976	0.558–1.677	0.929	0.949	0.605–1.484	0.820

^aYDQ: Young's Diagnostic Questionnaire.