Background: Aspects of the school environment, such as school attachment levels, are linked to adolescent offending. Previous research has not clarified whether a school‐ or individual‐level intervention approach to improving pupil school attachment and commitment is most likely to reduce adolescent offending. Aim: The present study assessed the impact of individual‐ and school‐level variables on offending behaviour from ages 14–16 years. Sample: The participants were 4,049 young people from 42 mainstream schools who took part in the Belfast Youth Development Study. Method: Multilevel modelling was used to examine the relative influence of individual‐ and school‐level variables on offending behaviour in adolescence. Results: Pupils who had high levels of school commitment and attachment and were involved in fewer fights at age 13 reported lower levels of offending at age 14 years. Differences between schools accounted for 7% of the variation in offending. Lower individual‐level commitment was associated with higher initial levels of offending at age 14 if the school‐level ethos was of higher commitment. Lack of safety at the school level appeared to be detrimental for young people not exposed to socio‐economic deprivation. Conclusions: Individual‐level targeted interventions are likely to be a more cost‐effective approach of reducing offending behaviour in adolescence. Additional, albeit smaller, reductions in offending levels could be achieved through school‐level interventions in some school types (e.g., deprived areas).

Background: Novel psychoactive substances (NPSs) contribute to the public health impact of substance misuse. This report provides research evidence addressing 11 research questions related to NPSs, covering types, patterns and settings of use; supply sources; and implications for policy and practice.Methods: The study used a conceptually linked three-phase mixed-methods design with a shared conceptual framework based on multiple-context risk and protective factors. Phase 1 was a quantitative phase involving secondary data analysis of the longitudinal Belfast Youth Development Study (BYDS), a latent class analysis using the 2039 BYDS participants. Phase 2 was an extensive qualitative analysis via narrative interviews with participants, sampled from BYDS, drug/alcohol services and prisons, to explore NPS use trajectories. Phase 3 was the final quantitative phase; generalisability of the shared risk factor part of the model was tested using the manual three-step approach to examine risk factors associated with latent class membership. The quantitative and qualitative analyses were integrated, thus allowing emerging findings to be further explored.Results: The data suggest that NPSs have a place within a range of polydrug use trajectories. Models showed no distinctive NPS class, with no clear evidence of differential risks for NPS use compared with the use of other substances. From the qualitative analysis, a taxonomy of groups was derived that explored how and where NPSs featured in a range of trajectories. This taxonomy was used to structure the analysis of factors linked to use within a risk and protective framework. Drivers for use were considered alongside knowledge, perceptions and experience of harms. Suggestions about how interventions could best respond to the various patterns of use – with special consideration of synthetic cannabinoids (SCs), including how they relate to the use of heroin and the potential for NPSs to operate as a ‘snare’ to more problem use – were also presented.Limitations: The study was conducted during 2016/17; generalisability beyond this sample and time point is limited. The level of missing data for some of the BYDS analysis was a limitation, as was the fact that the BYDS data were collected in 2011, so in a different context from the data collected during the narrative interviews. The Psychoactive Substances Act 2016 (Great Britain.Psychoactive Substances Act 2016. London: The Stationery Office; 2016) came into force during qualitative fieldwork and, although not particularly influential in this study, may be influential in future work. It is acknowledged that many of the data related to SCs and mephedrone. Although drug use was measured by self-report, the strength of rapport within interviews, reflective diaries and methodological acceptability checks helped to mitigate self-report bias.Conclusions: NPSs continue to present significant challenges for legislation and monitoring, researching and developing interventions. Understanding of usage patterns remains poor, with most information based on populations and settings where problems have already occurred. This research contributes to the evidence base by providing much needed further empirical data on the lived experiences of NPS users across a range of settings. In the light of these data, implications for policy and practice are discussed.Future work: Future research must generate improved epidemiological data on the extent, patterns and motivations for use longitudinally. The uniqueness of the information concerning SC use points to a specific set of findings not evidenced in other literature (e.g. intensity of SC withdrawal). Future research should focus on the symbiotic link between SC and heroin use.Funding: The National Institute for Health Research Public Health Research programme.

Aims: To provide public health‐related research evidence on types and usage patterns of new psychoactive substances (NPS), developmental pathways into NPS and decision‐making factors for, and associated harms of, NPS use.Design: Three‐phase mixed‐methods design, including a latent class analysis (LCA) of the longitudinal Belfast Youth Development Study (BYDS), a narrative analysis of interviews with NPS users and a three‐step approach manual method modelling using regressions to reveal classes of substance use and their associated predictors and outcomes.Setting: Northern Ireland.Participants: A total of 2039 people who responded to the questions on ‘ever use’ of the drug variables included at wave 7 (aged 21 years) of the BYDS. Eighty‐four narrative interviews with NPS users.Measurements: Categories of drug use identified by LCA. Predictors and outcomes included measures of family, partners, peers, substance use, school, delinquency and mental health.Findings: A four‐class solution provided the best fit for the data: alcohol; alcohol and tobacco; alcohol, tobacco and cannabis; and polydrug (the latter including NPS). The qualitative analysis yielded a taxonomy that distinguished how NPS operate within a wider range of drug repertoires from experimental to problematic.Conclusions: In Northern Ireland, new psychoactive substances appear to be a feature of broader polydrug use rather than a standalone class of drug use.