Background: Previous research has shown that exposure to bullying is linked to long-term adverse mental health consequences. However, prospective studies examining the persistence of bullying, using information from repeated time points, are limited. The aim of this study was to examine, firstly, the extent to which exposure to bullying among adolescents in Sweden changes between grades 9 (age 15-16) and 11 (age 17-18) (i.e., before and after the transition from lower to upper secondary school); secondly, whether being bullied in grade 9 or 11 is associated with depression and anxiety symptoms at age 20-21; and thirdly, if being bullied in both grade 9 and 11 is linked to an even higher likelihood of subsequent depression and anxiety symptoms. Potential differences by gender were investigated throughout.

Methods: Data was derived from the Swedish cohort study Futura01 involving individuals attending grade 9 in the school year 2016/17 (n = 2323). We utilised self-reported information from three survey waves conducted in 2017, 2019, and 2022, and linked registry information on sociodemographic characteristics. Bullying was assessed using a single item in waves 1 and 2. Depression and anxiety symptoms were measured using the Patient Health Questionnaire-4 (PHQ-4) in wave 3. Gender stratified binary logistic regressions were performed.

Results: Among those who were bullied in grade 9, 22.6% of males and 35.8% of females continued to experience bullying in grade 11. For females, exposure to bullying in grade 9 or 11 was associated with an increased likelihood of reporting depression and anxiety symptoms at age 20-21, with the highest odds for those bullied at both time points. For males, only one statistically significant association was identified - specifically, between being bullied in grade 9 and subsequent depression symptoms.ConclusionsFor a majority of adolescents who experience bullying in lower secondary school, but not all, the transition to upper secondary school proves to be beneficial as the bullying typically does not persist. However, bullying can have long-term health effects, in particular for females. These findings emphasise the importance of effective measures to address bullying within schools.