Table 1 Operationalization of TFA constructs for this study

Affective attitude

“How an individual feels about taking part in an intervention”

How much the youth enjoyed/or did not enjoy participating in the BI and interacting with the peer provider.

Burden

“The perceived amount of effort required to participate in the intervention (time, expense, and cognitive effort)”

What was easy or hard to understand about the BI content. Perceptions about the duration of the BI session.

Perceived effectiveness

“The extent to which the intervention is perceived as likely to achieve its purpose.”

How helpful the BI was. Any changes to substance use, relationships with family and friends, finances etc. following the BI.

Ethicality

“The extent to which the intervention has good fit with an individual’s value system”

How well the BI fit in with the youths’ goals and life plans. How well the BI aligned with the youths’ culture and values.

Intervention coherence

“The extent to which the participant understands the intervention, and how the intervention works”

The youths’ views about the goals of the BI.

Opportunity cost

“The extent to which benefits, profits, or values must be given up in the order to participate in an intervention”

Changes that the youth had to make to their schedules e.g. work and school to be able to participate in the BI.

Self-efficacy

“The participant’s confidence that they can perform the behavior required to participate in the intervention”.

How confident the youth who received the BI were in being able to reduce or stop using substances in the future?