Table 8.

Mapping the TBP constructs that predict e-cigarette use and intentions onto the TDF, intervention functions and suitable BCTs for inclusion in the intervention

TPB constructs	Predictors of intentions for eachTBP constructs	TPB constructs mapped onto the TDF	Intervention function	BCTs to be used to address intervention functions	APPEASE criteria	Content examples
Intentions	To use e-cigarettes in the next month	Intentions	Education Persuasion Incentivisation Coercion Modelling	Information about the health consequences. Antecedents Information about social and environmental consequences of behaviour	Yes Yes No No Yes	Encourage young people to intend to abstain from e-cigarette use. Refusal rehearsal. Embed abstention from e-cigarette use within the School.
Attitudes	Fun Cheap Safe Less likely to get into trouble with parents	Beliefs about consequences Knowledge	Education Persuasion Modelling	Information about the health consequences. Antecedents Information about social and environmental consequences of behaviour	Yes Yes Yes	Provide information on: -health implications of e-cigarette use and non-use. - outline links to nicotine and addiction smoking. Use media to identify examples of people to imitate or aspire to that do not use e-cigarettes.
Subjective norms	Friends Family Parents Medics	Social influences	Restriction Environmental restructuring Modelling Enablement	Restructuring the physical environment Demonstration of behaviour Social support Problem solving Action planning	Yes Yes Yes Yes	Raise awareness of social contexts that might lead to opportunities for experimenting with e-cigarettes. Social support to prevent use. Encourage others to abstain Reduce social acceptability.Provide information to parents on risk of e-cigarette use in young people. Raising awareness of parental roles in preventing uptake. Raising awareness of the need to restrict access to e-cigarettes in the home. Monitoring behaviour.
PBC: • Self-efficacy	Facilitators: Parent permission Curiosity Owning one Friends owning one Being cool Barriers: Parent getting into trouble Illegal purchase	Beliefs about capabilities	Education Persuasion Modelling Enablement	Information about health consequences Antecedents Information about social and environmental consequences of behaviour Demonstration of behaviour Social support Problem solving Action planning Restructuring the physical environment	Yes Yes Yes Yes	Enhance refusal self-efficacy Impart skills required to say no to e-cigarette experimentation Suggest to parents to discourage their children from using e-cigarettes via an information leaflet on their role in health behaviours
• Control beliefs		Environmental context & resources	Training Restriction Environmental restructuring enablement	Restructuring the physical environment	No Yes Yes Yes	Provide information on legislation around the use of e-cigarettes in young people. Raise safety concerns about e-cigarettes bought online. Create the expectation that there is a cost or punishment associated with the use of e-cigarettes. Embed these components in a school-based policy around the use of e-cigarettes in school

APPEASE criteria include considerations around affordability, practicability, effectiveness and cost-effectiveness, acceptability, side-effects/ safety and equity