An Analysis of Age and Gender Influences on the Relative Risk for Suicide & Psychotropic Drug Self- Poisoning AH Dawson 1, NA Buckley 2, IM Whyte 1, P Hazell 3, A Meza 4, H Britt 4 (1) Depart. of Clinical Toxicology, Newcastle Mater Hospital NSW, (2) Discipline of Clinical Pharmacology, Univ of Newcastle (3) Discipline of Psychiatry, Univ of Newcastle, (4) Family Medicne research Unit, Univ of Sydney

Background  Psychiatric illness is a significant risk factor for both attempted and completed suicide  Psychotropic medications account for 80% of all drug overdoses involving prescription medications  Age and gender have been suggested to be predictive of successful suicide (esp elderly males)  Information about the relative risk of overdose in subgroups of the population may assist in the decision to treat and in the choice of an appropriate psychotropic agent  Can the benefit of treatment be balanced against the risk of drug overdose

Aims  To compare the age and gender distribution of patients prescribed psychotropic drugs with patients attempting and completing suicide with these drugs Hypothesis  If the relative risk of self-poisoning per prescription is the same across the population, then the rate of self-poisoning in different age and gender groupings should reflect the prevalence of prescription of these drugs

Study Data Subset Psychotropic drugs (antipsychotic, antidepressant, sedative and anxiolytic drugs) Adults (age >14) Newcastle area (postcodes ) Demographic: Australian 1991 census: Hunter data Toxicology: Newcastle Clinical Toxicology self-poisoning database. Newcastle forensic database Prescription: Australian Morbidity and Treatment Survey (AMTS) Encounter based survey involving a random sample of 495 general practitioners who recorded details regarding over 100,000 doctor/patient encounters Data Sources

Results  The odds ratio (ORs) for self-poisoning were higher for < 45 years & yet this group was least likely to be prescribed psychotropic drugs  Males had a much higher rate of completed suicide using more lethal methods  The ORs for self-poisoning and suicide with psychotropic drugs, after correction for prescription rates  aged 15 to 24 were 11.1 and 1.7 respectively  aged 25 to 44 had ORs of 4.9 and 4.3  aged 75+ had ORs of 0.03 and 0  Females were slightly more likely to poison themselves with psychotropic drugs (OR 1.2), however the situation reversed after correction for prescription rates (OR 0.69)

Conclusions  Greater caution should be exercised in prescribing for those under 45, given their relatively higher risk of drug overdose, and the least toxic compounds should be used  The risk (of self-poisoning) in the elderly may have been overstated, so that some patients may have been denied the benefit of adequate treatment

Discussion  Some prescriber groups including psychiatrists were not included in the sampling group of doctors for the AMTS database. However:  Over 80% of antidepressant and antipsychotic prescriptions and 95% of sedative/hypnotic drug prescriptions are written by general practitioners (HIC data)  There were no differences between these drug classes and even if an additional 5% of sedative/hypnotic prescriptions were all written for the under 45 aged group this would not account for the observed difference  The self poisonings only include those who presented to hospital or reported to the coroner  It is plausible that a number of suicides might be certified as death from other causes. However the proportion of suicides due to poisoning was about a fifth across all age groups with the major difference being the type of poisons used, thus under the reporting of suicide by poisoning is unlikely to explain the observed differences