An Analysis of Age and Gender Influences on the Relative Risk for Suicide & Psychotropic Drug Self-Poisoning AH Dawson1, NA Buckley2, IM Whyte1,

P Hazell3, A Meza4, H Britt4

(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 SubsetPsychotropic drugs (antipsychotic, antidepressant, sedative and anxiolytic drugs)Adults (age >14)Newcastle area (postcodes 2280-2310)

Demographic: Australian 1991 census: Hunter data

Toxicology: Newcastle Clinical Toxicology self-poisoning database. Newcastle forensic database

Prescription: Australian Morbidity and Treatment Survey 1990-1991 (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