Intentional drug overdose: an examination of demographic, clinical and drug-related factors using national surveillance data

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Daly, Caroline
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University College Cork
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Background: Intentional drug overdose (IDO) is the most common method of hospital-presenting non-fatal self-harm internationally and is a common method of suicide. Those who engage in non-fatal IDO will often repeat self-harm (1, 2) and IDO confers a 40-fold increased risk of suicide (3). Individuals who engage in IDO are most commonly female, under 30 years of age, and they often consume alcohol and take multiple drugs in IDO (2, 4-6). Psychotropic and analgesic drugs are the most frequently used drugs in IDO (4, 7-9). Research illustrates parallels between the drugs people take in IDO and their availability at an individual and population level (9-14). There are major knowledge gaps in relation to a number of areas, in particular the specific types of drugs used in IDO and variations by individual demographics, the temporal trends of drugs types taken in IDO, the factors associated with fatality following IDO and repeated self-harm and method switching following IDO. The overarching aim of this thesis was to provide a comprehensive understanding of the demographic, clinical and drug-related factors associated with IDO. Methods: This research involved five pharmacoepidemiological studies, utilising two national datasets. These five studies comprised registry-based retrospective cohort studies examining hospital-presenting non-fatal IDO in the Republic of Ireland using data from the National Self-Harm Registry Ireland (NSHRI). In addition, one study (Study 3) also incorporated data on suicides obtained from the National Drug-Related Deaths Index Ireland (NDRDI). Analyses in this thesis included Poisson regression, Cox proportional hazard regression modelling, joinpoint regression modelling, Kaplan Meier survival analysis and data weighting. Results: Study 1 identified analgesics, antidepressant and sedative drugs as the most frequently used in IDO with significant variations in drug types used by gender and age profiles. The contribution of alcohol in Ireland (41%) was identified to be lower than comparative countries however multiple drug IDO involvement was significantly higher (47%). Study 2 demonstrated a tenfold increase in the use of gabapentinoids between 2007 and 2015 and established the potential severity of these IDOs in terms of quantities of tablets taken and recommended next care. Study 3 established male gender, increasing age and multiple drug use as factors associated with fatal IDO outcome and found that tricyclic antidepressants (TCAs) and opioid drugs were associated with significantly high risk of death. Study 4 described the increasing incidence of paracetamol-related IDOs among young people (9% increase between 2007 and 2018) and established that the most significant increase occurred among females aged 18-24 years, with a contrasting decrease observed among males of the same age. Findings from Study 5 showed that risk of repeat self-harm following IDO among young people was highest for males, those aged 10-17 years and those who took ≥50 tablets or antidepressants and benzodiazepines in IDO. In addition, method switching was found to be significantly associated with being male and taking illegal drugs in an index IDO presentation. Conclusion: The findings from this thesis provide unique insights into the demographic, clinical and drug-related profiles of individuals who engage in hospital-presenting IDO. Important emerging trends in the use of specific drugs in IDO have been examined. This research has identified the risk factors associated with repeat self-harm, method switching and fatality following IDO, of which several are modifiable. Furthermore, this research presents key implications for prescribing, means restriction interventions, training of healthcare and allied professionals and the provision of optimised care to patients within healthcare settings.
Self-harm , Suicide , Drug , Overdose
Daly, C. 2020. Intentional drug overdose: an examination of demographic, clinical and drug-related factors using national surveillance data. PhD Thesis, University College Cork.