Table 4.

Mean scores of Mood Inventory subcomponents according to overall quartiles of hours of mobile phone use per week stratified by sex

Mood Inventory subcomponents	Hours of mobile phone use per week				P for trenda	P valuesb (ANCOVA)	Bonferroni’s multiple comparison (P < 0.05)
	Quartile 1: <10 h/week	Quartile 2: 10–18 h/week	Quartile 3: 19–32 h/week	Quartile 4: ≥33 h/week
Female	N = 366	N = 396	N = 445	N = 480
Tension and excitement	13.7 (3.9)	13.8 (3.8)	13.8 (3.8)	14.3 (3.8)	0.150	0.336	–
Refreshing mood	14.0 (2.8)	14.0 (2.9)	14.0 (2.8)	13.9 (2.8)	0.440	0.842	–
Fatigue	15.6 (4.0)	15.9 (3.8)	16.0 (3.7)	16.6 (3.9)	<0.028	0.156	–
Depressed mood	15.5 (4.9)	15.9 (5.0)	15.4 (4.6)	16.4 (4.9)	0.257	0.075	–
Anxious mood	17.5 (5.0)	17.9 (4.7)	17.5 (4.7)	18.0 (4.5)	0.592	0.557	–
Male	N = 375	N = 226	N = 246	N = 164
Tension and excitement	14.0 (4.4)	13.8 (4.2)	14.4 (4.1)	15.6 (4.3)	<0.001	<0.001	Quartile 1 vs. quartile 4; quartile 2 vs. quartile 4; quartile 3 vs. quartile 4
Refreshing mood	13.8 (2.8)	13.8 (2.8)	13.9 (2.7)	13.9 (2.5)	0.841	0.995	–
Fatigue	15.2 (4.1)	15.6 (3.7)	15.6 (3.7)	16.5 (4.1)	<0.001	<0.004	Quartile 1 vs. quartile 4
Depressed mood	15.3 (5.4)	14.8 (5.1)	15.2 (4.8)	16.8 (5.2)	<0.007	<0.002	Quartile 1 vs. quartile 4; quartile 2 vs. quartile 4; quartile 3 vs. quartile 4
Anxious mood	17.4 (5.3)	16.5 (4.9)	17.5 (5.0)	18.4 (4.8)	<0.046	<0.006	Quartile 2 vs. quartile 4

Data are presented as the mean with the SD in parenthesis

^aTested by multiple regression analysis, adjusted for school year, participation in sports club activities, mobile phone use experience, hours spent sleeping, and schools

^bTested by ANCOVA, adjusted for school year, participation in sports club activities, mobile phone use experience, number of hours spent sleeping, and schools