The present review protocol is being reported in accordance with the reporting guidance the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P) statement  (see PRISMA-P checklist in Additional file 1). This review protocol was registered within the International Prospective Register of Systematic Reviews (PROSPERO) (registration number CRD42019123812).
Criteria for considering studies for this review are classified by the following:
In order to meet inclusion criteria, studies must involve an evaluation of implementation strategies used to transfer an evidence-based psychosocial treatment or treatment guideline into clinical practice in SUD settings. Psychosocial treatments include any attempt to affect change in patients’ substance use through behaviour, cognition, affect, interpersonal relationships or environment (e.g. employment, housing). Participants in these studies may include any clinician providing psychosocial interventions to SUD patients accessing outpatient or inpatient drug and alcohol services. ‘Clinician’ is defined as an individual employed to implement change in SUD patients’ substance use using psychosocial treatments exclusively. As such, studies will be excluded from the review if they focus on the development of psychometric instruments, drugs in sport, harm prevention or community awareness.
The psychosocial intervention must be evidence-based and provide clear recommendations for practice. Studies will be excluded if they involve physiological, pharmacological or education-based interventions. Information including the nature of desired change, strategies employed, source of the intervention, mode of delivery (individual or group), identification of who delivered the intervention and the timing, duration, and frequency of the intervention needs to be stated clearly. Only ethically approved studies will be considered.
Comparator and study design
Only studies with a comparison group will be included. Comparisons may be made before and after the administration of the intervention, between two or more forms of intervention, or between different types of intervention(s) (or no intervention). We will include randomised controlled trials (RCTs), non-randomised controlled trials, observational studies including before-and-after studies, and time series analyses.
Primary study outcomes will be related to the implementation, service system or clinical practice. Specifically, outcomes will include infidelity, attitudes toward or satisfaction with the intervention (acceptability), and adoption, appropriateness of the intervention to the target population, implementation costs, the feasibility of the intervention within the setting, and the sustainability of the intervention after implementation. The length of post-intervention follow-up period must be specified and any possible ceiling effects identified. Outcomes will be related to the effectiveness of the implementation process, as distinct from the efficacy of the intervention itself.
Since SUD inpatient and outpatient treatment settings that provide counselling services to patients are the focus of the review, settings such as primary care, criminal justice or those investigating cross-cultural factors will be excluded from the review.
The following electronic databases will be searched (from inception onwards): PubMed/MEDLINE, Cochrane Library, PsycINFO, Web of Science and CINAHL. Additionally, we will conduct reference searches of relevant reviews and articles. Similarly, a grey literature search will be done with help of Google and the Grey Matters tool which is a checklist of health-related sites organised by topic. The tool is produced by the Canadian Agency for Drugs and Technologies in Health (CADTH) .
The search will include all relevant peer-reviewed studies. The search will be conducted across 4 relevant concepts (see draft strategy in Additional file 2): (1) implementation, (2) evidence-based practices, (3) substance use service setting/drug and alcohol service setting and (4) eligible research designs. Specific terms used to search these concepts will be adapted from a recent systematic review conducted in the mental health field . The MEDLINE draft search strategy is available in Additional file 2.
Selection and data extraction
Two reviewers will screen all articles identified from the search independently. First, titles and abstracts of articles returned from initial searches will be screened based on the eligibility criteria outlined above. Second, full texts will be examined in detail and screened for eligibility. Third, references of all considered articles will be hand-searched to identify any relevant report missed in the search strategy by two reviewers independently. Any disagreement between reviewers will be resolved by discussion to meet a consensus. EndNote version X9 (Clarivate Analytics) will be used to manage all records.
Two researchers will extract data and organise it into variables based on the Cochrane Effective Practice and Organisation of Care Review Group (EPOC) Data Abstraction Form (e.g. clinical interventions, strategies, outcomes and results), the conceptual model of Proctor et al.  (implementation, service system and clinical outcomes), information about any specific implementation frameworks used, and a checklist of items aligned with the domains and subdomains of the CFIR (i.e. subdomains associated with intervention characteristics, outer setting, inner setting, characteristics of individuals and the implementation process). This method was used effectively in two previous reviews [23, 34] as a means of categorising the types of implementation strategies addressed by each of the studies included in the review.
Risk of bias of individual studies
All included studies will be critically evaluated by two researchers independently using the Revised Cochrane risk-of-bias tool (RoB 2) . The RoB 2 provides a systematic assessment across five domains of bias (the randomisation process, deviations from intended interventions, missing outcome data, measurement of the outcome and selection of the reported results) to assess quality of the article per outcome. For cluster-randomised studies, an additional domain must be used when assessing the randomization process. Any non-randomised studies of interventions will be assessed using the ROBINS-I tool is a risk of bias tool .
We do not anticipate having sufficient studies for a meta-analysis and therefore plan to perform a narrative synthesis. The main methods of synthesis will most likely involve tabulation, textual descriptions, qualitative synthesis of themes and vote-counting . We will synthesise the findings from the included articles using the CFIR framework. If any issues requiring sensitivity analyses arise during the review process, such analyses will be conducted.
Meta-biases such as outcome reporting bias will be evaluated by ensuring that a protocol was published prior to the recruitment of participants. Trial registries will also be checked to determine the integrity of reported outcome measures and statistical methods. The grey literature search may also assist with identifying publication bias.
Confidence in cumulative evidence
Strength of the evidence will be graded according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach . In the event that there is disagreement between the two reviewers, a third researcher will be consulted.