Comorbidity of serious mental illness and type 2 diabetes: do neighbourhoods matter?

Background: Serious mental illness (SMI) refers to mental disorders that are severe in degree, persistent and produce considerable functional impairment, and include conditions such as schizophrenia, bipolar disorder or major depression. Type 2 diabetes (T2D) is 2 - 4 times more prevalent in people with SMI and contributes significantly to the increased morbidity and mortality experienced by this group. Even though antipsychotic medication is recognised as a major risk factor for T2D in individuals with SMI, there are likely additional biopsychosocial mechanisms involved that may independently contribute to SMI-T2D comorbidity. One possible correlate that has not been adequately investigated in this context is the neighbourhood environment. There is strong evidence that people with SMI are more likely to live in socioeconomically disadvantaged neighbourhoods with poorer resources and infrastructure. These neighbourhood influences have been associated with traditional risk factors of diabetes such as inactive lifestyle, unhealthy food choices and obesity. Despite the plausibility, little evidence is available on the associations of neighbourhood contextual factors with SMI-T2D comorbidity. Aims: The principal aims of this thesis were threefold. First, to describe the geography of SMI-T2D comorbidity in the Illawarra-Shoalhaven region of NSW, Australia. Second, to explore the cross-sectional association between neighbourhood-level socioeconomic disadvantage and SMI-T2D comorbidity. Third, to identify the specific features of disadvantaged neighbourhood environments that are associated with SMI-T2D comorbidity.