Using the Network Approach to Psychopathology to Better Understand the Complex Relationships between Depressive Symptoms with Risk Factors, Suicidality, and Inflammation amongst Pacific Young People in New Zealand

Abstract

Depression is the leading cause of disability worldwide and is closely associated with suicidality (suicidal thoughts, plans or attempts), many serious physical health conditions, and actual suicide. Depression, and suicide are problems in New Zealand (NZ), which has higher depression prevalence and teen suicide rates than many similar high-income countries. Within NZ, the burden of depression and suicidality is disproportionate, affecting some groups more than others. Pacific adolescents and Pacific young adults in NZ show significantly higher rates of depressive symptoms, psychological distress and suicidality compared to NZ European adolescents. Despite these elevated risks little research has been conducted into depression and suicidality amongst this population.

This thesis applied the network approach to psychopathology to investigate various aspects of depressive symptomatology amongst NZ Pacific adolescents and young adults, specifically associations between individual depression symptoms with risk factors, suicidality and inflammation. According to the network perspective, the symptoms and their interactions comprise the disorder rather than being manifestations of a common cause. Using this approach, depression is measured in terms of individual symptoms (although it may also be measured complementarily in other ways) and the associations amongst the individual depression symptoms and between the symptoms and other relevant non-symptom factors are visualized in a highly intuitive network graph. The overall aim of this thesis was to use the network approach, to gain a deeper insight into these complex and multi-faceted relationships. To fulfil this objective, three original studies and a literature review were conducted. The first part of this thesis focused primarily on associations between psychosocial risk factors with depression and suicidality, with two original studies. One study investigated associations between depression symptoms with a wide range of multi-dimensional potential risk factors for depression. The second study was an in-depth investigation into associations between suicidality with individual depression symptoms and self-harm. Both studies broke new ground being the first time that the network approach had been used to investigate depression risk factors or suicidality amongst Pacific adolescents in NZ. The second part of the thesis moved to investigate possible biological correlations with depression and specifically focused on the inflammation - depression relationship. This included conducting a literature review and an original study into associations between depression and inflammation amongst Pacific young adults. The original study represented the first time that links between depression and inflammation had been examined for Pacific New Zealanders of any age.

The results were illuminating. Measuring depression in terms of individual symptoms and the additional statistical acuity derived from analysing network topology revealed a more nuanced and dynamic understanding of the relationships under study, which also revealed potentially culturally shaped findings. The results from the original studies also suggested possible targets for clinical interventions and information that could be used to shape prevention strategies and treatment plans. Overall, the primary hope from this thesis is that the information obtained has clinical usefulness, which will aid the treatment of depression and suicidality amongst Pacific young people. Secondarily, it aims to add empirical weight to calls for re-evaluation of the prevailing ways depression is measured, including within research frameworks, clinical environments, and education and health settings.