Editor—Our critical finding was the relation between decline in suicide rate and exposure to antidepressants across age groups in both sexes. We agree that time series data must be interpreted cautiously; that is why we considered alternative explanations.
We disagree with Moncrieff that we should have used ratios of daily dependent doses. This would have been an alternative measure of change in exposure but not of overall antidepressant exposure. We agree that the daily dependent doses will underestimate prescribing levels of tricyclic antidepressants in elderly patients but believe that this would underestimate any correlation between antidepressant prescribing and suicide trend by underestimating elderly exposure to antidepressants.
The fact that, as Verberne and Draper point out, suicide rates in older people declined before the period of increase of the selective serotonin reuptake inhibitors does not mean antidepressants could not be a contributory cause of the decline in suicide rates between 1991 and 2000. Suicide rates in young men did not decrease, yet antidepressant prescribing increased over the same period, albeit from a very low base, as Ankarberg says. We accept that using antidepressants is not the only influence in suicides among young men.
It is true that meta-analyses of placebo controlled randomised controlled trials have not shown a lower rate of suicide among patients receiving antidepressants, as Ankarberg says. However, patients at risk of suicide are often excluded from such studies. These studies often entail follow up periods of less than six months so their findings do not necessarily apply to the general population.
This letter is also written by the other authors: Valerie A Rendle (project officer, School of Public Health and Community Medicine, University of New South Wales), Ian B Hickie (chief executive officer, beyond blue: the national depression initiative, Melbourne, Victoria 3122, Australia), and Peter McManus (formerly secretary, Drug Utilisation Sub Committee Department of Health and Ageing, Canberra 2601, Australia).
Competing interests: AM was a consultant on Quality Use of Medicines to Merck, Sharp and Dohme Australia (1997), has been a member of advisory boards for Pfizer and Sanofi-Synthelabo (1999-2000), and was sponsored to attend Global Health Care 2000 Conference (Eli-Lilly). PBM has received research funding and honorariums in the past five years from several pharmaceutical companies that manufacture antidepressant medications. IBH has received research funding and honorariums in the past five years from several pharmaceutical companies for conduct of general practice training programmes and from Wyeth for participation in international meetings detailing the economic and social costs of depression.