Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Mortality
[20] Systematic review	576 people 4 RCTs in this analysis	Mortality 3/287 (1%) with methadone maintenance treatment 8/289 (3%) with no methadone maintenance treatment	RR 0.48 95% CI 0.10 to 2.39 P = 0.37		Not significant