Leveraging process models of self-regulation to understand unassisted smoking cessation

Project Summary/Abstract
Unassisted smoking cessation (i.e., quitting without formal support) remains common yet under-researched. This thesis explores unassisted quitting through motivation and self-regulation theories, using mixed methods to examine why and how people quit on their own.
Chapter 1 sets the public health context in the UK and introduces a theoretical framework drawing on Self-Determination Theory, the Health Belief Model, and self-regulation. It also proposes the concept of "polyregulation", i.e., using multiple strategies to support behaviour change.
Chapter 2 presents a qualitative study of 32 unassisted quitters, analysed using reflexive Thematic Analysis. Motivations were shaped by life events, identity shifts and a desire for autonomy, challenging binary views of internal vs. external motivation.
Chapter 3 explores the strategies used to quit, applying the Process Model of Self-Control and the Behaviour Change Taxonomy. Participants described a diverse behavioural "toolbox," including environmental restructuring, distraction and cognitive reappraisal, highlighting the sophistication of unassisted attempts and supporting the concept of polyregulation.
Chapter 4 analyses survey data from 498 quitters. Notably, unassisted quitters reported more autonomous motivation. Although low SES was generally linked to lower motivation and fewer strategies, unassisted quitting appeared to buffer against this trend.
Chapter 5 follows 226 quitters over 12 weeks. While autonomous motivation predicted greater strategy use, neither variable significantly predicted cessation outcomes.
Chapter 6 uses multiverse analysis to test the robustness of these findings. Results confirmed weak associations with outcomes, though T1 perceived competence consistently predicted lower T2 nicotine dependence.
Chapter 7 synthesises findings, proposing a profile of the unassisted quitter as strategically autonomous and shaped by identity shifts. Implications and future directions are discussed.