Psychopathology in response to multiple population stressors

Abstract

A series of large-scale social unrest and co-occurring COVID-19 have erupted in Hong Kong during early 2020. How population-level and personal stressors can interact with intrinsic factors to affect mental health as the events evolve remains to be elucidated.

Three symptom dimensions with varying degrees of responsiveness to external stressors were examined throughout this thesis: PTSD and depressive symptoms (more reactive) and psychotic-like experiences (PLEs; typically considered to be more endogenous), with a key focus on ideas of reference (IOR). Event-based rumination, defined as repetitive thoughts about external events, and smartphone overuse were hypothesised to be transdiagnostic mediators between different stressor types and all three psychopathological states.

Using timely data collected through a large-scale locally adapted online tool, Study 1 (n = 10,110) revealed that social unrest-related traumatic events (TEs), COVID-19 events, and personal stressful life events (SLEs) additively and interactively contributed to PTSD and depressive symptoms. Notably, event-based rumination was significantly associated with both symptom dimensions and mediated the effects of all three event types. The predictive capability of event-based rumination for one-month PTSD and depressive symptoms amid such ongoing population-level stressors was further demonstrated in Study 2 (n = 150), highlighting its clinical significance.

Study 3 (n = 9,873) provided novel evidence in showing that IOR experiences, as a form of PLEs, could also be triggered by population-level stressors. While extrinsic factors, such as severe TEs and SLEs, played more prominent roles in attenuated IOR (feeling of being particularly referred to) and intrinsic factors, such as cognitive ability, played more prominent roles in exclusive IOR (feeling of being exclusively referred to), event-based rumination was associated with both spectra of IOR.

With a wider range of environmental and personal risk and protective factors considered, Study 4 (n = 9,688) highlighted the transdiagnostic effects of not only event-based rumination but also smartphone overuse. Some support was found for both these factors as serial mediators between extrinsic events and all three symptom outcomes, although most of the effects were explained by event-based rumination. Smartphone overuse may possibly contribute to symptoms via a separate pathway.

Furthermore, the transdiagnostic effects of event-based rumination and smartphone overuse remained robust in both Study 5 (n = 6,988), using data from a large subgroup of young people further collected through the tool, and in Study 6 (n = 669), using data from an epidemiological youth sample collected one year later (during which TEs have subsided and COVID-19 was ongoing). Using path analysis, the mediating effects of event-based rumination between extrinsic events and IOR severity were again supported, with some of the effects of SLEs on both event-based rumination and IOR severity explained by individual subjective stress.

Finally, Study 7 offered initial evidence suggesting IOR experiences as a higher class of psychopathology. Symptom network analysis revealed that event-based rumination also contributed to specific symptom-level associations between IOR and both PTSD and depressive symptoms.

The increasingly observed co-occurring large-scale crises globally demands valid, context-relevant, agile, and timely action. It is hoped this thesis could inform such future work.