Table 1. Demographic, academic, life style and health-related characteristics of the total sample and gender subsamples.

Demography	Total (N = 903)	Males (N = 357)	Females (N = 546)	P
School type (%)
Vocational high school	46.5	51.3	43.4	0.021
Gymnasium	53.5	48.7	56.6
Living standard (%)
Low	7.0	6.5	7.3	0.032
Average	81.8	78.9	83.7
High	11.2	14.6	9.0
School achievement
School grades (1 - 5)	4.02 ± 0.69	3.90 ± 0.74	4.10 ± 0.65	< 0.001
School behavior (%)
Misconduct	2.9	5.3	1.3	< 0.001
Good	11.3	14.9	9.0
Exemplary	85.8	79.8	89.7
Social life
Having a best friend (%)	93.2	89.3	95.8	< 0.001
Having a boyfriend/girlfriend (%)	36.4	31.2	39.7	0.009
Health related practices
Self-rated health (1 - 5)	3.96 ± 0.76	4.11 ± 0.77	3.86 ± 0.75	< 0.001
Self-rated healthiness of diet (1 - 5)	3.70 ± 0.83	3.72 ± 0.86	3.70 ± 0.81	0.738
Frequency of physical exercise (%)
Doesn’t exercise at all	19.0	7.0	26.7	< 0.001
Rarely, up to once a week	26.8	20.2	31.1
Regularly, two to three times a week	34.7	41.6	30.2
Every day	19.5	31.2	11.9
Number of sexual partners so far	0.94 ± 1.36	1.38 ± 1.67	0.65 ± 1.01	< 0.001
Alcohol consumption (%)
Slight (up to several times a year)	63.2	49.9	71.9	< 0.001
Moderate (up to several times a month)	33.4	43.4	26.8
Heavy (several times a week or more)	3.4	6.7	1.3
Smoking (%)
Never or almost never	59.6	67.5	54.4	< 0.001
Rarely (up to several times a week)	16.1	13.5	17.8
Frequently (daily)	24.3	19.1	27.8
Drug abuse (%)
Never or just once	76.3	71.6	79.4	0.007
Several times a year or more	23.7	28.5	20.6
Data are expressed as percentage (%) and mean + standard deviation (SD). Differences between males and females were calculated using the t-test and the χ2 test. P < 0.05 was considered statistically significant.