This thesis examines three main themes; depression, suicidality, and non-fatal overdose involving pharmaceutical and over-the-counter (OTC) medications. At any given time depression affects approximately one in every twenty adults in Australia. People with depression are at elevated risk of attempted and completed suicide compared to those without. Medication overdose is a frequently chosen method of suicidal behaviour, and accounts for one in ten suicide deaths and close to nine out of ten non-fatal episodes of suicidal behaviour for which hospital treatment is sought. The study reported here had six primary aims; (i) to quantify medication overdose presentations over a 12-month period to the Emergency Department (ED) of a major metropolitan public hospital in Melbourne, Australia, (ii) to describe the medication overdose patient group, including comparison with two other relevant types of presentation, illicit drug overdose, and actual or potential self-harm by means other than overdose, (iii) to explore the relationship between depression, suicidal ideation and medication overdose, (iv) to identify the medications typically used in overdose and their means of acquisition, (v) to explore patient experiences of emergency care following a medication overdose, and (vi) to comment on the feasibility of introducing a brief intervention within the ED with the intention of addressing the issue of medication overdose. Three data sources were employed: computerised ED records, interviews with a sub-sample of patients attending the ED following a medication overdose, and observation of ED processes in relation to these cases. / One of the most important findings of the study was the large contribution made by benzodiazepine medications to the overall medication overdose statistics. When considered in conjunction with the patient interview data, it appeared that many patients included in the study were prescribed benzodiazepines in a manner that contradicts current national prescribing guidelines. The problem of medication overdose could be partially addressed by working with doctors to ensure the appropriateness of their prescribing practices, to encourage them to more closely monitor the treatment progress of at-risk patients, and to increase awareness of other evidence-based forms of treatment for depression and anxiety.

Opioid drug related death is the topic of this thesis. Each of the published works submitted in this volume has investigated an aspect of opioid drug related death. The publications have been grouped into three sub-themes: i. Characteristics of opioid drug related deaths ii. Methadone-related deaths in and out of treatment iii. Improving the quality of treatment for opioid drug dependence: a focus on injectable opioid treatment The introduction and background (Chapter1) will briefly review-the-relevant literature on opioid drug death predating my own contribution to the field. The next chapter of the thesis, 'Publications' (Chapter 2), will comprise the body of published work being submitted for the degree of Doctor of Medicine. Each article is accompanied by text on the preceding page outlining my individual contribution to that research study. The thesis will conclude with a discussion of the published works (Discussion, Chapter 3) which summarises the chief findings and reflects on the international significance and impact of the work. Finally, the Conclusion (Chapter 4) will submit suggestions for areas of future research into opioid drug related death.