Changes over time in mental health symptoms among adolescents in Tampere, Finland.

Background: Mental health problems are common in adolescence and seeking help for them is becoming more common. Referrals to adolescent mental healthcare have recently increased in Finland.

Objective: To examine time trends in internalizing and externalizing mental health symptoms among Finnish adolescents.

Method: A time-trend school survey was conducted among 9^th graders (15-year-olds) in Tampere, Finland, in three time periods: 2002-03, 2012-13 and 2018-19 (N = 4,162).

Results: Compared to the period 2002-03, prevalence of externalizing symptoms decreased in the period 2012-13 and further in 2018-19. The prevalence of internalizing symptoms did not change significantly between 2002-03 and 2012-13; however, in 2018-19, depression, social anxiety, general anxiety, poor subjective health, stress symptoms among boys, and poor self-esteem increased compared to earlier time periods. The increases were more marked among girls. However, suicidal ideation did not increase in 2018-19 compared to earlier time periods.

Conclusion: Whereas the prevalence of externalizing symptoms decreased among Finnish adolescents between 2002-03 and 2018-19, the prevalence of internalizing symptoms increased between 2012-13 and 2018-19. To help to understand the causes of these increases and to prevent internalizing problems, further research on the underlying causes is needed.