Young et al. BMC Public Health 2011, 11:874 http://www.biomedcentral.com/1471-2458/11/874 even a small effect may have a pervasive influence, since contextual factors may influence the behaviour of an entire community, rather than a single individual. In this paper we explore the association between the school (school connectedness, denomination, school ethos, size of school) and suicide-risk, adjusting for important background factors, such as perception of local neighbourhood and prior mental health risk. Our data are derived from a longitudinal study of approxi- mately 1700 young people followed from age 11 to 19, located within 43 different schools and their associated neighbourhoods. We frame our analysis using three theories relevant to contextual influences on suicidal behaviour; the Ecological-transactional model; Durkheim’s anomic- egoistic theory and Joiners transpersonal theory of sui- cide. However, before outlining each theory, we briefly review the relevant literature on major contextual influences on suicide, how these are conceived, mea- sured and the potential difficulties inherent in contex- tual analysis. Neighbourhood, contextual effects and suicide Contextual influences on suicide rates are well known: rates of suicide vary by access to firearms and geogra- phical location, [4] and concepts such as anomie (the disconnect between individual and societal norms and expectations) are classic contextual explanations of sui- cide [5]. A number of studies have investigated the phe- nomenon of geographical clustering in young adult [6] and teenage suicides [7]. Although the mechanisms involved in the epidemiology of suicide clusters are still unclear, if one excludes the possibility of contagion, explanations of contextual effects can be putatively linked to standard risk factors such as social inequalities, inequalities in social capital or ‘social connectedness’, cultural or religious differences and statistical artefact due to compositional effects [1]. In relation to self harm, some studies have found rates of hospitalisation due to self harm to be higher in deprived areas [8-10], but a large part of contextual effects seem attributable to compositional factors. Neighbourhood and school influences on mental health The neighbourhood is associated with a variety of child and adolescent health outcomes. A systematic review of multi-level studies estimated that, after accounting for individual and family characteristics, neighbourhood determinants explain approximately 10% of the variance in child and adolescent health outcomes [11]. How young people themselves perceive and experience their local physical and social neighbourhood (e.g. the degree of attractiveness or level of amenities) is related to a range of mental health outcomes [12,13]. Page 2 of 15 Studies which explore the contextual influence of school on suicidal behaviour and self-harm are rare, although we can extrapolate to a degree from school studies of substance use [14] and wellbeing [15]. When reviewing the influence of school from a multilevel con- text including four studies of ‘problem behaviour and wellbeing’ outcomes, the intra class correlations (ICC; the percent of variance attributable to contextual influ- ence) never exceeded 8% and most were below 4% [15]. Therefore, it is likely that the contribution of school in relation to suicidal behaviour is small, but nonetheless important given the severity of the outcome and the implications for policy development. School connectedness, school ethos and school context Positive orientation to school, teacher support, school engagement, school attachment, school bonding, school climate, school involvement, and school connectedness are all terms that refer to the attachment individual pupils have to the school and which have been mea- sured with a variety of scales [16]. Although there are differences in focus, most of these questionnaires argu- ably tap a similar underlying construct we term school connectedness. School connectedness is associated with many health behaviours [17], among them measures of psychological distress and suicidality. For example, a recent study of school factors among Norwegian adoles- cents found teacher support strongly predicted lower depressive symptoms both cross-sectionally and longi- tudinally at one-year follow-up [18]. Compared to school connectedness, the concept of school ethos is more nebulous, described by Hughes [19] as “... a convenient word to use about a school, as long as one doesn’t define it.” It generally refers to the overall school culture, atmosphere or climate - arguably equally vague terms. Despite measurement problems, many researchers consider school ethos important, with ethos operationalised as the sum effect of school processes and relationships [3]. A composite measure of school ethos was constructed for previous analyses of the data- set used in this paper using multiple indicators [14]. Factor analysis of a range of pupil-reported school-based items produced four measures: school environment (e.g. quality of the physical environment); pupil involvement (e.g. feeling part of the school); pupil (dis)engagement (e.g. dislike of school); and quality of teacher-pupil rela- tionships (e.g. number of ‘good’ teacher/pupil relations). Measured at the individual level, these can be consid- ered forms of school connectedness or engagement, when measured at the school level they are more accu- rately described as indicators of school ethos, and accordingly, these four variables were aggregated across all pupils in each school to produce an overall contex- tual ‘school ethos’ measure. Each measure significantly