Table 1.

Overview of studies included.

First author, date	Study location	Participant dependence status	N (dependent)
Alcohol, n = 11
Alba-Ferrara 2016	California, USA	Early (<12 months) or sustained (>12 months) remission	10
Charlet 2014	Mannheim, Germany	4–24 days abstinent	33
Gilman 2008	Maryland, USA	3 weeks abstinent	12
Jansen 2019	Amsterdam, Netherlands	Minimum 3 weeks abstinent	39
Kim 2014	Seoul, South Korea	3–21 days abstinent	38
Marinkovic 2009	Massachusetts, USA	4 weeks abstinent	15
O’Daly 2012	London, UK	Minimum 2 weeks abstinent	29 (12 MSDs)
Salloum 2007	Maryland, USA	Mean 28 days since last drink ± 15 days	11
Seo 2013	Connecticut, USA	4–8 weeks abstinent	45
Zakiniaiez 2017	Connecticut, USA	4–6 weeks abstinent (mean 34 days)	45
Yang 2013	Texas, USA	3–5 weeks abstinent	15
Cocaine, n = 6
Albein-Urios 2014	Grenada, Spain	Minimum 15 days abstinent	17
Asensio 2010	Valencia, Spain	72 hours abstinent	32
Canterberry 2016	USA (unspecified)	Not stated	20
Potenza 2012	Connecticut, USA	Minimum 2 weeks abstinent	30
Sinha 2005	Connecticut, USA	Minimum 2 weeks abstinent	20
Xu 2013	Connecticut, USA	2–4 weeks in treatment	67
Opioids, n = 4
Schmidt 2014	Basel, Switzerland	Maintained on heroin for at least 6 months	22
Schmidt 2015	Basel, Switzerland	Maintained on heroin for at least 6 months	22 (as above)
Wang 2010	Shantou, China	Abstinent 2–5 months	17
Smoski 2011	Washington, USA	Maintained on buprenorphine/naloxone for average 14.8 weeks	12
Cannabis, n = 3
Wesley 2016	Kentucky, USA	Abstinent the day of scanning	16
Wetherill 2014	Pennsylvania,	Self-reported abstinence 1.5 ± 1.5 days	20
Zimmermann 2018	Bonn, Germany	At least 28 days abstinent	19

Abbreviations: MSD medically supervised detoxification, USA United States of America.