Silverman 2020.

Study characteristics
Methods	Study design: cluster RCT Study grouping: parallel group Allocation concealment: method for allocation concealment not specified Randomisation method: throughout 24 sessions, the researcher cluster‐randomised people on the unit into experimental or control conditions by session. The numbers 1–24 were randomised into 2 groups and each group was assigned to either the experimental or control condition. Participants were allocated the group of the first session they attended.
Participants	Baseline characteristics MT + SC Gender male: 44 (63%) Age: 35.43 years Sample size: 70 SC (wait‐list control) Gender male: 44 (71%) Age: 34.45 years Sample size: 62 Overall Gender male: 88 (67%) Age: 34.94 years Sample size: 132 Inclusion criteria: adult inpatient on detoxification unit (meeting diagnostic criteria for substance dependency); ability to read English. Exclusion criteria: none mentioned Pretreatment: no significant differences between groups in regard to: total number of times participants had been admitted to a substance abuse facility; days on the unit; number of patients taking part in each session who volunteered to be research participants; total number of participants in each session; age; gender; ethnic background; drug of choice.
Interventions	Intervention characteristics MT + SC Description: MT group songwriting session with focus on theme of perceived stigma and perceived social support (using blues genre). Session length: 45 minutes Frequency: single session Duration of treatment: single session SC (wait‐list control) Description: wait‐list control Session length: not applicable Frequency: not applicable Duration of treatment: not applicable
Outcomes	Not used: Perceived stigma (Perceived Stigma and Addiction Scale (PSAS)); Perceived social support (the Multidimensional Scale of Perceived Social Support (MSPSS))
Identification	Sponsorship source: none Country: USA Setting: inpatient detoxification unit of a large teaching hospital Author's name: Michael J Silverman Institution: University of Minnesota Email: silvermj@umn.edu Address: Music Therapy, University of Minnesota, Minneapolis, Minnesota, USA Declarations of interest: no conflicts of interest reported.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Judgement comment: throughout 24 sessions, the researcher cluster‐randomised people on the unit into experimental or control conditions by session. The numbers 1–24 were randomised into 2 groups and each group was assigned to either the experimental or control condition.
Allocation concealment (selection bias)	Unclear risk	Judgement comment: information on allocation concealment not specified.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Judgement comment: missing outcome data balanced in numbers across intervention 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	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 not likely to be influenced differentially between groups.