Methodological and Conceptual Advances in Understanding Psychological Flexibility as a Modifiable Protective Factor for Suicidal Thoughts and Behaviours

Suicide is a global public health issue. Cross-nationally, many people experience suicidal thoughts and behaviours (STBs). Much is known about the risk factors of STBs; for example, as depicted by the Integrated Motivational Volitional (IMV) Model. However, modifiable protective factors remain relatively under-researched. Psychological factors which underlie existing intervention packages, such as psychological flexibility. Psychological flexibility is purported to be the therapeutic process of change underlying an existing intervention package – Acceptance and Commitment Therapy. Broadly, this PhD explored whether psychological flexibility had a potentially protective role for STBs. Four original studies designed this evidence gap were conducted. A large, three-wave longitudinal survey with adults from the online general population laid the conceptual groundwork for this thesis on proximal risk. Testing the IMV model cross-sectionally and longitudinally using structural equation modelling confirmed that the IMV’s central path was empirically sound. The full model with motivational moderators showed poor model fit, perhaps explainable by methodological and statistical challenges discussed. Psychological flexibility, particularly valued actions and behavioural awareness were moderate-to-strong cross-sectional and longitudinal correlates of proximal risk factors, and possibly volitional moderators. The natural stability of the constructs suggests that experimental, intervention work is needed to fully test the theorised effect of psychological flexibility as a protective factor for proximal risk of STBs. Study 2 examined the acceptability of five values clarification exercises (VCEs) using an online randomised, active-controlled experimental trial. Adults with recent experience of suicidal thoughts provided invaluable open-ended feedback on the acceptability of the VCEs, informing a tailored, single-session VCE. Study 2 also found preliminary evidence that the VCEs improved state value clarity, the therapeutic ...