Building A Syndemic Model of Severe Mental Illness Experience: The Relationship Between Modifiable Health Behaviours and Health Experience in Vulnerable Populations

Background: Syndemics describes the synergistic interaction of two or more co-occurring epidemics, creating synergistically combined health impacts. This thesis examined a Syndemic model of health experience via health behaviours (physical activity, addiction related behaviour, resilience, exposure to nature, sleep), socio-political indicators, and health outcomes in vulnerable populations.

Methods: Based on Syndemic Framework Theory, a Syndemic model was developed and tested using secondary data from two major UK cohorts: the UK Biobank (UKBB), including cross-sectional data from adults with severe mental illness (N = 8,014), and the Avon Longitudinal Study of Parents and Children (ALSPAC), including longitudinal childhood and adolescent data (N = 15,645). Structural Equation Modeling (SEM) was used to analyse the relationships between the health behaviours, socio-political indicators, and health experience.

Results: UKBB: While all health behaviours and socio-political indicators except addiction-related behaviours significantly affected health experience (p ≤ 0.023; p = 0.742), some model fit indices were below standard cut-off scores (CFI = 0.815, TLI = 0.786; RMSEA = 0.051, SRMR = 0.037). The Syndemic model was partially supported; physical activity, exposure to nature, sleep, and resilience demonstrated significant mutual associations (p ≤ 0.001), though addiction related behaviour did not (p ≥ 0.538). ALSPAC: While most childhood and adolescent health behaviours and parental socio-political indicators significantly affected health experience (p ≤ 0.046), model fit indices were below standard cut-off scores (e.g., CFI = 0.628, RMSEA = 0.132). Notably, all health behaviours were significantly associated with one another across development, and longitudinal analysis confirmed behavioural stability from childhood into adolescence between select behaviours (p ≤ 0.036).

Conclusions: These results suggest partial support for a Syndemic model of health experience. However, the varying relationships and model fit issues suggest that further research is required to refine the hypothesised Syndemic model across vulnerable populations.