Date of Award


Embargo Period


Degree Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Associate Professor Darren Morton

Second Advisor

Dr Jason Morton


4203 Health services and systems| 4206 Public health


The prevalence of depression and anxiety before the COVID-19 pandemic was estimated at 586 million worldwide, and this figure has subsequently increased. The current paradigm for preventing and managing mental health is predicated primarily on pharmacotherapy. This approach is not working, and there are urgent calls to use integrated non-pharmacological strategies. Studies have demonstrated the effectiveness of lifestyle medicine and positive psychology interventions to enhance mental health and wellbeing. However, no randomized controlled trial (RCT) has examined the effectiveness of a digital multicomponent interdisciplinary intervention for improving mental health and wellbeing in a nonclinical setting. In addition, the literature is sparse in understanding the gender and age responsiveness to digital mental wellbeing interventions.

This thesis utilised two experimental studies (Study 1, randomized controlled trial, n=421; and Study 2, a randomized comparative study, n=458) to assess the effectiveness of a ten-week digital multicomponent interdisciplinary mental wellbeing intervention that used Persuasive System Design (PSD), principles and combined strategies from lifestyle medicine and positive psychology. The participants completed a questionnaire at baseline and post-intervention that assessed their mental health, vitality, depression, anxiety, stress, life satisfaction, and flourishing. Study 1 also included follow-up at 12 weeks post-intervention. Intervention adherence and engagement were also assessed. This thesis presents the findings of the studies in a coherent series of publications in scholarly journals and highlights several significant findings.

First, the digital multicomponent interdisciplinary mental wellbeing intervention significantly improved all mental health and wellbeing measures amongst the Australasian nonclinical cohort. The outcomes measures remained significant at 12 weeks post-intervention for the intervention group. Second, the studies observed larger effect sizes than previous studies that utilised single-modality interventions, suggesting that a multicomponent interdisciplinary approach may yield compounding benefits. Third, gender and age did not influence adherence to the intervention that employed PSD principles to improve mental health and wellbeing.

Last, the studies reported low attrition rates compared to the existing literature, which typically finds adherence and attrition problematic for digital delivery. In summary, a digital multicomponent interdisciplinary mental wellbeing intervention that uses a lifestyle medicine and positive psychology approach, and employs PSD principles, can significantly increase mental health and wellbeing across gender and age groups. Amid COVID-19 pandemic, there is an urgent need to implement interventions at a population-level–such as the one used in this thesis–that are cost-effective and easily disseminated. This thesis informs a potential way forward.

Creative Commons License

Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License


Used by permission: the author.

Staff and Students of Avondale College may access a print copy of this thesis from Avondale College Library (SC Theses 362.19689 P95).