Objectives: To establish the relation between recurrent peer victimisation and onset of self reported symptoms of anxiety or depression in the early teen years. Design: Cohort study over two years. Setting: Secondary schools in Victoria, Australia. Participants: 2680 students surveyed twice in year 8 (aged 13 years) and once in year 9. Main outcome measures: Self reported symptoms of anxiety or depression were assessed by using the computerised version of the revised clinical interview schedule. Incident cases were students scoring ≥12 in year 9 but not previously. Prior victimisation was defined as having been bullied at either or both survey times in year 8. Results: Prevalence of victimisation at the second survey point in year 8 was 51% (95% confidence interval 49% to 54%), and prevalence of self reported symptoms of anxiety or depression was 18% (16% to 20%). The incidence of self reported symptoms of anxiety or depression in year 9 (7%) was significantly associated with victimisation reported either once (odds ratio 1.94, 1.1 to 3.3) or twice (2.30, 1.2 to 4.3) in year 8. After adjustment for availability of social relations and for sociodemographic factors, recurrent victimisation remained predictive of self reported symptoms of anxiety or depression for girls (2.60, 1.2 to 5.5) but not for boys (1.36, 0.6 to 3.0). Newly reported victimisation in year 9 was not significantly associated with prior self report of symptoms of anxiety or depression (1.48, 0.4 to 6.0). Conclusion: A history of victimisation and poor social relationships predicts the onset of emotional problems in adolescents. Previous recurrent emotional problems are not significantly related to future victimisation. These findings have implications for how seriously the occurrence of victimisation is treated and for the focus of interventions aimed at addressing mental health issues in adolescents. What is already known on this topic: Being bullied is a common experience for many young people Victimisation is related to depression and, to a lesser extent, anxiety, loneliness, and general self esteem Debate remains as to whether victimisation precedes the onset of emotional problems or whether young people with emotional problems “invite” victimisation What this study adds: A history of victimisation predicts the onset of anxiety or depression, especially in adolescent girls Previous recurrent emotional problems are not significantly related to future victimisation Reduction in bullying in schools could have a substantial impact on the emotional wellbeing of young people

Public health interventions aim to improve the health of populations or at-risk subgroups. Problems targeted by such interventions, such as diet and smoking, involve complex multifactorial aetiology. Interventions will often aim to address more than one cause simultaneously, targeting factors at multiple levels (eg, individual, interpersonal, organisational), and comprising several components which interact to affect more than one outcome.1 They will often be delivered in systems which respond in unpredictable ways to the new intervention.2 Recognition is growing that evaluations need to understand this complexity if they are to inform future intervention development, or efforts to apply the same intervention in another setting or population.1 Achieving this will require evaluators to move beyond a ‘does it work?’ focus, towards combining outcomes and process evaluation. There is no such thing as a typical process evaluation, with the term applied to studies which range from a few simple quantitative items on satisfaction, to complex mixed-method studies exploring issues such as the process of implementation, or contextual influences on implementation and outcomes. As recognised within MRC guidance for evaluating complex interventions, process evaluation may be used to ‘assess fidelity and quality of implementation, clarify causal mechanisms and identify contextual factors associated with variation in outcomes’.1 This paper briefly discusses each of these core aims for process evaluation, before describing current Medical Research Council (MRC) Population Health Sciences Research Network (PHSRN) funded work to develop guidance for process evaluations of complex public health interventions.

Objectives. We sought to test the efficacy of an intervention that was designed to promote social inclusion and commitment to education, in reducing among students health risk behaviors and improving emotional well-being. Methods. The design was a cluster-randomized trial in 25 secondary schools in Victoria, Australia. The subjects were 8th-grade students (aged 13 to 14 y) in 1997 (n=2545) and subsequent 8th-grade students in 1999 (n=2586) and 2001 (n=2463). The main outcomes were recent substance use, antisocial behavior, initiation of sexual intercourse, and depressive symptoms. Results. At 4-year follow-up, the prevalence of marked health risk behaviors was approximately 20% in schools in the comparison group and 15% in schools in the intervention group, an overall reduction of 25%. In ordinal logistic regression models a protective effect of intervention was found for a composite measure of health risk behaviors in unadjusted models (odds ratio [OR]= 0.69; 95% confidence interval [CI]= 0.50, 0.95) and adjusted models (OR= 0.71; CI =0.52, 0.97) for potential confounders. There was no evidence of a reduction in depressive symptoms. Conclusion. The study provides support for prevention strategies in schools that move beyond health education to promoting positive social environments.

Study objective: The aim of this study was to determine the effect of a multilevel school based intervention on adolescents’ emotional wellbeing and health risk behaviours. Design: School based cluster randomised controlled trial. Students were surveyed using laptop computers, twice in the first year of intervention and annually thereafter for a further two years. Setting: Secondary schools. Participants: 2678 year 8 students (74%) participated in the first wave of data collection. Attrition across the waves was less than 3%, 8%, and 10% respectively with no differential response rate between intervention and control groups at the subsequent waves (98% v 96%; 92% v 92%, and 90% v 89% respectively). Main results: A comparatively consistent 3% to 5% risk difference was found between intervention and control students for any drinking, any and regular smoking, and friends’ alcohol and tobacco use across the three waves of follow up. The largest effect was a reduction in the reporting of regular smoking by those in the intervention group (OR 0.57, 0.62, and 0.72 at waves 2, 3, and 4 respectively). There was no significant effect of the intervention on depressive symptoms, and social and school relationships. Conclusions: While further research is required to determine fully the processes of change, this study shows that a focus on general cognitive skills and positive changes to the social environment of the school can have a substantial impact on important health risk behaviours.