Occurrence of violence among 12-18-year-old adolescents in 1999 and 2009 in Finland.

We examined whether the occurrence of violence changed among Finnish adolescents between 1999 and 2009. The study was based on the nationwide Adolescent Health and Lifestyle Survey from samples of 12- to 18-year-olds. The number of respondents was 8136 in 1999 and 5516 in 2009.