Crimes by gang members have serious social and economic impacts. A new Campbell systematic review assesses interventions to 
reduce gang membership and rehabilitate gang members in low- and middle-income countries (L&MICs).
The Campbell review had two objectives:
1) To examine evidence on the effectiveness of interventions to prevent youth involvement in gangs and gang crime in LMICs, and
2) To identify the reasons why preventive interventions succeed or fail
No studies assessing the effect of preventive gang interventions in L&MICs were identified. So the review is not able to provide conclusions on which interventions are most effective.
Four studies evaluating reasons for the implementation success or failure of preventive interventions were reviewed indicating that preventive gang interventions may be more likely to be successfully implemented when they include
- program components which appeal to youth
- provide continuity of social ties outside of the gang
- recognition that ongoing violence and gang involvement can hinder successful implementation, and
- active engagement of youth
The review highlights the lack of robust evidence related to preventive programs. A rigorous programme of evaluations should be developed for these interventions.