Table 5.

Retention in treatment.

First Author, Year, Country	Population Studied	Retention in Treatment Outcome
Bakker, 2017, UK [19]	GP practice OAT case note review (n = 278)	Treatment retention for patients on BZD maintenance treatment was over twice as long as that compared with patients never on BZD prescription (mean of 72 months vs. 34 months between groups).
Durand, 2021, Ireland [21]	Specialist treatment clinics (n = 2035)	BZD in previous 90 days increased treatment dropout rates at 12 months (HR 1.22, 95% CI 1.03–1.45) but not at 3 months (HR 1.03, 95% CI 0.88–1.21).
Eibl, 2019, Canada [22]	Clinic population (n = 3692)	1-year treatment retention non-prescribed BZD users were two times as likely (adjusted OR 0.38, 95% CI 0.27–0.53) to discontinue treatment as those not using BZD or those using prescribed BZD.
MacLeod, 2019, UK [24]	Primary care OAT, England (n = 12,118)	Concurrent prescription of BZD was associated with increased duration of methadone treatment (adjusted mean duration of treatment episode 466 days [95% CI 450 to 483] compared to 286 days [95% CI 275 to 297]) and for buprenorphine, 234 [95% CI 217 to 250]).
Maremmani, 2014, Italy [25]	(n = 77)	No differences in survival-in-treatment rates (0.44 vs. 0.58).
Park, 2020, USA [28]	Buprenorphine OAT (n = 63,345)	BZD treatment during buprenorphine treatment was associated with a decreased risk of buprenorphine treatment discontinuation (HR 0.87, 95% CI 0.85–0.89).
Schuman-Olivier, 2013, USA [30]	(n = 328)	No statistically significant differences in 12-month retention in treatment based on past-year BZD use BZD Rx or the combination.