Using Formal and Computational Modelling to Develop an Initial Within-Person System Dynamics Model of Relapse in Smoking Cessation: A Participatory, Iterative, Multi-Method Approach

Popular relapse prevention theories are represented using natural language descriptions and lack temporal information about how phenomena of interest (i.e., ‘relapse’, ‘prolapse’, ‘abstinence’) are dynamically caused over time and within individuals. We drew on the Theory Construction Methodology to develop a formal and computational model of relapse in smoking cessation. We used a participatory, iterative, multi-method approach involving an informal theory and computational model review, stakeholder interviews with researchers, people with lived experience, stop smoking practitioners, and policymakers (N = 15) and in silico simulations. We propose an initial within-person system dynamics model of relapse (‘COMPLAPSE’) in which biopsychosocial factors (e.g., stressors, cigarette cues, cravings, self-efficacy) are represented as time-varying inputs and state variables. These factors jointly determine the momentary preference for each behavioural option (i.e., smoke a cigarette, use a regulatory strategy, do nothing), with the probability of selecting each option (i.e., the output) generated by a softmax function. The simulations highlight the model’s ability to generate representational patterns of relapse, prolapse and abstinence, thus providing an early sense-check of its explanatory adequacy. In addition, local sensitivity analyses demonstrate that systematic variation of selected model parameters leads to expected qualitative shifts from, for example, prolapse to relapse. We discuss the implications of our work for relapse prevention theories and real-world applications, including the development and optimisation of technology-mediated just-in-time adaptive interventions for relapse prevention in smoking cessation.