Silverman 2011a.

Study characteristics
Methods	Study design: cluster RCT Study grouping: parallel group Allocation concealment: not specified Randomisation method: participants in 28 sessions were randomised into experimental or control conditions by session. The numbers 1–28 were randomised into 2 groups and each group was assigned to a condition.
Participants	Baseline characteristics MT + SC Gender male: 33 (47.82%) Age: 43.33 years Sample size: 69 Verbal therapy + SC Gender male: 37 (52.11%) Age: 43.07 years Sample size: 71 Overall Gender male: 70 (50%) Age: 43.2 years Sample size: 140 Inclusion criteria: inpatients in an adult detoxification unit Exclusion criteria: none specified Pretreatment: no significant differences between groups in regard to: number of consumers taking part in each session who volunteered to be research participants; total number of consumers in each session; participants' ages. Confirmation of population eligibility (from study author): author confirmed that participants had diagnosis of SUD.
Interventions	Intervention characteristics MT + SC Description: MT songwriting group session focused on change and led by board‐certified music therapist. Therapeutic techniques manualised using the functional CBT manual provided by Cather 2005. Session length: approximately 45 minutes Frequency: single session Duration of treatment: single session Verbal therapy + SC Description: non‐music verbal group focused on change led by same therapist. Therapeutic techniques manualised using the functional CBT manual provided by Cather 2005. Session length: approximately 45 minutes Frequency: single session Duration of treatment: single session
Outcomes	Self‐report depression (BDI) Outcome type: continuous outcome Scale: 4‐point scale (0–3) for each item Range: 0–63 Direction: lower is better Data value: endpoint Notes: BDI–II. 21‐item self‐report test measuring current level of depression. Range reported in related literature. Higher scores indicate higher levels of depression. Depression – self‐report via Likert‐type scale Outcome type: continuous outcome Reporting: partially reported Scale: 7‐point Likert‐type scale Range: 1–7 Direction: lower is better Data value: endpoint Notes: researcher‐developed 7‐point Likert‐type scale to assess self‐reported current level of depression. Motivation for change – URICA Contemplation subscale Outcome type: continuous outcome Reporting: partially reported Scale: 5‐point Likert‐type scale for each item Range: 8–40 Direction: higher is better Data value: endpoint Notes: each subscale has 8 items (1 indicates strong disagreement, 5 strong agreement). Higher scores on URICA indicate greater readiness for change. Composite score is available, but author only reported subscales. "The subscales can be combined arithmetically (C + A + M – PC) to yield a second‐order continuous Readiness to Change score that can be used to assess readiness to change at entrance to treatment. Motivation for change – URICA Action subscale Outcome type: continuous outcome Reporting: partially reported Scale: 5‐point Likert‐type scale for each item Range: 8–40 Direction: higher is better Data value: endpoint Notes: composite score for URICA is available, but author only provided scores for subscales. Substance use – self‐report Outcome type: dichotomous outcome Reporting: partially reported Direction: higher is better Data value: endpoint Notes: researcher was able to contact 56 participants at 1‐month follow‐up. Participants were asked if they had maintained their sobriety, with the response options of: yes, somewhat, and no. This variable was scored here as a dichotomous variable with 'no' scored for both 'somewhat' and 'no' responses.
Identification	Sponsorship source: none Country: USA Setting: inpatient detoxification unit Author's name: Michael J Silverman Institution: University of Minnesota Email: silvermj@umn.edu Declarations of interest: no conflicts of interest reported.
Notes	Email (13 September 2017) from author confirmed that participants met criteria for SUD.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Judgement comment: participants in 28 sessions were randomised into experimental or control conditions by session. The numbers 1–28 were randomised into 2 groups and each group was assigned to a condition.
Allocation concealment (selection bias)	Unclear risk	Judgement comment: insufficient information about allocation concealment to permit judgement.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Judgement comment: missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups. Reasons for missing outcome data unlikely to be related to true outcome.
Selective reporting (reporting bias)	Low risk	Judgement comment: no selective outcome reporting.
Blinding of participants and providers (performance bias) (subjective outcomes)	Low risk	Judgement comment: not possible to blind participants and providers to MT intervention.
Blinding of outcome assessor (detection bias) (subjective outcomes)	Unclear risk	Judgement comment: not possible to blind outcome assessor for self‐report outcomes, though measurement unlikely to be influenced differentially between groups.