Table 1.

Description of included studies on DRD, PUDP, PUDP, polydrug use, age of PUDP, and treatment coverage and efficacy, injecting drug use, treatment during incarceration, and social deprivation

No.	Sample	Time frame	Data source	Main results	Ref.
1	150,517	1996–2007	All people released from all Scottish prisons	Opioid substitution therapy in Scottish prisons decreased the rate of DRD by 40%	[19]
2	3,182	2006–2013	NRS	Scotland's National Naloxone Programme was associated with a 36% reduction in the proportion of ORDs	[18]
3	33,128	2009–2013	Scotland's Prescribing Information System and NRS	Higher methadone-specific DRD rates in older clients	[13]
4	3,262	2009–2015	NRS	Circulatory disease as comorbidity most likely implicated in the 4-fold increase of methadone-specific DRD risk at 45+ yrs	[14]
5	2,418	2007–2012	National databases for England and Wales	Buprenorphine is 6 times safer than methadone with regard to overdose risk	[20]
6	69,456	1996–2006	SDMD	Drug users, especially those HCV-diagnosed showed an increased mortality risk	[10]
7	69,457	1996–2006	Registration of drug treatment in Scotland	Discharge of people in treatment for drug dependence from hospitalization were at increased risk of DRD	[16]
8	3,850	2013–2014	PWID survey	15% of drug injectors reported overdosing during the preceding year	[15]
9	Not specified	1979–2013	NRS	Age-standardized rates for DRDs among young adults rose during the 1990s in Scotland, especially for males living in the most deprived areas	[11]
10	198,247	2005–2009	Drug treatment and criminal justice sources in England	Opioid users' excess mortality persists into old age	[8]
11	151,983	2005–2009	NDTMS and ONS	Patients receiving only psychological support for opioid dependence in England were at greater risk of DRD	[9]
12	1,266 DRDs	2005–2009	NDTMS	Sharp age-related increase in the risk of methadone-specific death in the UK	[12]
13	>98,000	1996–2010	SDMD	Hospital-discharge gives increased DRD vulnerability, especially for drug injectors	[17]
14	3,731	2008–2011	NDTMS and ONS	The English public treatment system for opioid use disorder prevented 880 deaths yearly from opioid-related poisoning	[21]

NRS, National Records of Scotland; SDMD, Scottish Drug Misuse Database; NDTMS, National Drug Treatment Monitoring System in England; ONS, Office for National Statistics in England; ORD, opioid-related death; PUDP, people using drugs in a problematic way; PWID, persons who inject drugs.