The prevalences were difference by sex (prevalence among males was 14, 25% and among females was 0, 08%), age (the prevalence increased from 15 years of age and increased most rapid during 18 - 22 years of age), type of school (one of students of regular schools was 1, 12%; vocational schools 15, 61% and universities 9, 51%), level of physical activities, occupation of fathers and place of birth.