Table 3.

A summary of the narrative analysis for included studies based on categories 1–3 of the theory coding scheme [27]

Study (country)	Category 1: Is theory mentioned?		Category 2: Are relevant theoretical constructs targeted by the intervention?		Category 3: Is theory used to tailor the intervention or select the intervention recipients?
	Yes, no, or partiallya	Reason	Yes, no, or partiallyb	Reason	Yes, no, or partiallyc	Reason
Barnason et al. [39] (USA)	Yesa	Met TCS item 1 and 3 Bandura’s SCT Met TCS item 2 Refer to category 2	Yesb	Met TCS item 2 Targeted constructs of SCT (e.g. self-regulation) were mentioned as predictors of adherence Met TCS item 5 Theory was used to select intervention techniques (e.g. self-monitoring selected based on self-regulation construct of SCT) Met TCS item 7 All intervention techniques were linked to theoretical constructs or predictors (e.g. verbal persuasion technique linked to self-efficacy) Met TCS item 10 Targeted constructs were linked explicitly to at least one intervention technique	Partiallyc	Met TCS item 6 Predictors (e.g. motivation) were examined via questionnaires and used to tailor the intervention to individual patients Did not meet TCS item 4 Intervention recipients were not selected using theory (e.g. based on ‘self-efficacy’ levels)
O’Carroll et al. [42, 48, 52] (UK)	Yesa	Met TCS items 1 and 3 Leventhal’s SRM (also made reference to Hall and Fong’s temporal self-regulation theory) Met TCS item 2 Refer to category 2	Yesb	Met TCS item 2 Targeted construct of SRM (‘illness perceptions’) was mentioned as a predictor of adherence Met TCS item 5 Theory was used to select intervention techniques Met TCS item 7 All intervention techniques were linked to theoretical constructs/predictors (e.g. information about health consequences was linked to illness perceptions) Met TCS item 11 Targeted constructs/predictors were linked explicitly to at least one intervention technique	Noc	Did not meet TCS item 6 Intervention was not tailored based on theory Did not meet TCS item 4 Intervention recipients were selected based on a self-report questionnaire score but not specifically using theory (e.g. based on illness perceptions)
Ruppar [40] (USA)	Yesa	Met TCS item 1 and 3 Leventhal’s SRM Met TCS item 2 Refer to category 2	Partiallyb	Met TCS item 2 Targeted construct (illness perceptions) was mentioned as a predictor of adherence behaviour Did not meet TCS item 5 Theory was not used to select all intervention techniques (e.g. prompts) Met TCS item 8 At least one, but not all, intervention techniques were explicitly linked to theoretical constructs (e.g. habit modification not linked to theory) Met TCS item 11 Key theoretical construct (illness perceptions) was linked to intervention techniques	Noc	Did not meet TCS item 6 Habit modification was tailored but not linked to theory Did not meet TCS item 4 Intervention recipients were not selected using theory (e.g. based on their illness perceptions)
Solomon et al. [38, 44] (USA)	Partiallya	Met TCS item 1 and 3 Prochaska’s TTM Did not meet TCS item 2 Refer to category 2	Nob	Did not meet TCS item 2 The authors did not explicitly indicate that the constructs of TTM (e.g. stage of change, process of change, self-efficacy) were predictors of adherence Did not meet TCS item 5 Theory did not appear to guide the selection of MI techniques. MI techniques appear to have been selected based on similar interventions and then linked back to theory Did not meet TCS item 7, 8 or 9 MI techniques were not directly linked back to constructs within the model Did not meet TCS item 10 or 11 Key constructs of TTM were not explicitly linked to MI techniques	Noc	Did not meet TCS item 6 The authors did report that MI is based on an ‘individual’s readiness for change’, but they did not link this to their own intervention Did not meet TCS item 4 Intervention recipients were not selected using theory (e.g. based on their ‘stage of change’)
Williams et al. [41, 57] (Australia)	Yesa	Met TCS item 1 and 3 HBM (modified) Met TCS item 2 Refer to category 2	Partiallyb	Met TCS item 2 Targeted constructs of the modified HBM were mentioned as predictors of adherence (e.g. self-efficacy) Did not meet TCS item 5 Theory was not used to select all intervention techniques (e.g. self-monitoring) Met TCS item 8 At least one, but not all, intervention techniques were explicitly linked to theoretical constructs (e.g. goal setting was not linked to constructs) Did not meet TCS item 10 or 11 Theoretical constructs were not explicitly linked to intervention techniques	Noc	Did not meet TCS item 6 MI was tailored but not linked to theory. Other intervention techniques were not tailored Did not meet TCS item 4 Intervention recipients were not selected using theory (e.g. based on their level of ‘self-efficacy’)

HBM health belief model, MI motivational interviewing, SCT social cognitive theory, SRM Self-Regulation Model, TCS theory coding scheme, TTM transtheoretical model

^aJudgement of ‘yes’ if study met TCS items 1, 2 and 3 in category 1. Judgement of ‘partially’ if study met any of the TCS items in category 1. Judgement of ‘no’ if study did not meet any TCS items in category 1

^bJudgement of ‘yes’ if study met TCS items 2 and 5 and 7, 8 or 9 and 10 or 11 in category 2. Judgement of ‘partially’ if study met any of the TCS items in category 2. Judgement of ‘no’ if study did not meet any TCS items in category 2

^cJudgement of ‘yes’ if study met TCS items 4 and 6 in category 3. Judgement of ‘partially’ if study met any of the TCS items in category 3. Judgement of ‘no’ if study did not met any TCS items in category 3