[Summary text]
Selection bias (biased allocation to interventions) due to inadequate generation of a randomised sequence
alone. Individual patients were allocated to each condition by a third party with no affiliation to the study who used a computer-generated randomization list stratified for sex and three types of substance use (alcohol alone, drugs alone, or drugs and alcohol) to ensure equal male-female and substance use representation in each arm of the trial.
Selection bias (biased allocation to interventions) due to inadequate concealment of allocations prior to assignment
Not described
Performance bias due to knowledge of the allocated interventions by participants and personnel during the study
Single-blinded
Detection bias due to knowledge of the allocated interventions by outcome assessors
The assessors were blind to treatment allocation; attempts to maintain their blind- ness included use of separate rooms and administrative proce- dures for project staff, multiple coding of treatment allocations, and requesting subjects not to disclose information about the treatment.
Attrition bias due to amount, nature or handling of incomplete outcome data
Not described
Reporting bias due to selective outcome reporting
Bias due to problems not covered elsewhere in the table