Bullying and mental health

Author: Martha R. Villabona works at Subdirección General de Cooperación Territorial e Innovación Educativa of the Spanish Ministry of Education and Vocational Training, where she coordinates the area of multiple literacies.

The relationship between experiences of bullying and serious mental health problems has been at the center of scientific debate for years. However, it is only in the last decade that longitudinal studies have made it possible to go beyond correlation and explore the direction and persistence of these effects over time. Two pieces of research—an international systematic review and a large European study—offer an updated and nuanced picture of how victimization impacts self-harm, suicidal ideation, and depression, and how, in turn, these problems can feed back into the dynamics of bullying.

The systematic review ¹ analyzed 35 studies from 17 countries and confirmed that both school bullying and cyberbullying consistently increase the likelihood of suicidal ideation and attempts, as well as non-suicidal self-harm. Effect sizes vary from weak to strong depending on the type of aggression and the follow-up window, but the pattern is clear: being the target of repeated attacks leaves a psychological mark that lasts beyond the end of the bullying.

Despite the strength of the main finding, the authors highlight several limitations that call for caution. There is heterogeneity in the definitions of bullying, the instruments used, and the follow-up periods. Only one in five publications analyzes sex/gender differences, and additional variables such as family adversity, personality traits, or prior mental health are controlled unevenly. For example, prior depression may increase the likelihood of being bullied (by showing withdrawal or low assertiveness) and, at the same time, increase the risk of suicidal ideation on its own. If the analysis does not determine this pre-existing depression, we will obtain an inflated relationship between bullying and suicidal ideation, attributing to the former an impact that was already partly predetermined by depression. Robust longitudinal studies introduce these variables into their models to isolate the effect of victimization itself and avoid misleading interpretations.

The second study ² followed 2,933 adolescents from 10 European countries assessed at three time points (0, 3, and 12 months). The authors observed a clear bidirectional effect: victimization predicts future depression, but baseline depression also increases the likelihood of subsequent bullying. In addition, they differentiate between chronic victimization (present in two consecutive measurements) and sporadic victimization. Those who suffered chronic physical bullying showed the highest risk of suicide attempts, while chronic relational aggression was mainly linked to suicidal ideation; one-off exposure only retained predictive power if it involved physical violence. This study reinforces the idea that chronicity—rather than the specific type of aggression—multiplies the risk, but it highlights the particular danger of physical violence, even if it occurs only once.

Taken together, the findings support the chronic interpersonal stress hypothesis: repetitive aggression interferes with reward circuits and undermines self-esteem. Self-harm then emerges as an emotional regulation strategy. Pre-existing depression, meanwhile, impairs social skills, making adolescents more vulnerable to new episodes of bullying.

Furthermore, the longitudinal review analyzed gender differences, suggesting that girls may be more sensitive to relational victimization and cyberbullying, translating that experience into non-suicidal self-harm and suicidal ideation. However, boys are more vulnerable to physical aggression that can lead to suicide attempts.

To reduce the risk of self-harm and suicidal ideation associated with bullying, the evidence highlights the need for an integrated approach that combines early detection and ongoing monitoring, recording not only the onset but also the persistence of bullying with programs that improve the school climate and include selective psychological support protocols for victims and adolescents with depressive symptoms. In addition, treating depression and strengthening social-emotional skills breaks the bidirectional link that makes psychopathology both a cause and consequence of bullying.

The authors of the review recommend standardizing definitions and instruments, extending follow-up beyond adolescence, and systematically introducing intersectionality variables (gender, sexual orientation, ethnicity). They also call for studies incorporating stress biomarkers and neuroimaging to clarify causal mechanisms and, above all, longitudinal evaluations of the real effectiveness of interventions against school bullying.

According to the authors, recognizing the chronicity and type of victimization allows for the definition of prevention measures, while understanding the bidirectionality with depression reminds us that caring for mental health is also a way to combat bullying.