Repetition Risk for Adolescent Self-Poisoning: A Multiple Event Survival Analysis

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Abstract
Objectives: To examine risk factors associated with re-presentation (event rates) following an initial episode of hospital treated self-poisoning. Method: A longitudinal cohort study using the Hunter Area Toxicology Service (HATS) database of all presentations to hospital of self-poisoned patients aged 10–19 in Newcastle and Lake Macquarie Regions of New South Wales from January 1991 to December 1995. The study factors were: age, gender, employment status, ‘substance abuse’ and psychiatric diagnosis at index (first documented episode during the study time-period) admission. The main outcome measure was re-presentations per unit time. Time-event analysis (multivariate) was used to compare re-presentation rates per person-year exposure to the study factors. Results: There were 450 patients who presented on a total of 551 occasions. The median and modal age at initial presentation was 17. Three hundred and nine (69%) were female and 141 (31%) were male. The probability (95% CI) of a patient re-presenting within one year of an index admission with self poisoning was 0.09 (0.07–0.12) and within 5 years was 0.16 (0.12–0.21). The adjusted rate ratios for episodes of re-presentation were: any ‘substance abuse (ever)’ 3.87 (2.08–7.21), ‘alcohol abuse’ 2.32 (1.15–4.68),‘benzodiazepine abuse’ 4.89 (1.63–14.62), schizophrenia and other psychotic disorders (DSM-IV) 2.85 (1.2–6.79), and any personality disorder (DSM-IV) 2.68 (1.73–4.16). Conclusions: Interventions to decrease recurrence rates for adolescent self poisoning should be directed towards substance (particularly alcohol or benzodiazepine) abuse, nonaffective psychoses and personality disorder.