A new research suggests that the suicide rates in England and Wales may be much higher than officially stated because the way coroners record deaths has evolved.
Professor David Gunnell at the University of Bristol and colleagues from the Universities of Oxford and Manchester say changes are needed urgently to ensure the future reliability of national suicide statistics.
Suicide accounted for 4,648 deaths in England and Wales in 2009. Official statistics produced by the Office for National Statistics (ONS) are currently based on suicide and open verdict deaths (known as "short form" verdicts) given by coroners after inquests into unnatural or unexpected deaths.
However, since 2001, a growing number of coroners have summarised their inquest findings with a "narrative verdict" - which records, in several sentences, how, and in what circumstances, the death occurred - rather than giving a short form verdict.
Narrative verdicts have some advantages. But, because they often do not mention intent, narrative verdicts can be difficult for the ONS to code, explain the authors - when suicide intent is unclear such deaths are classified as accidental.
The numbers of narrative verdicts increased from 111 in 2001 to 3,012 (more than 10 per cent of all inquests) in 2009, and figures for 2010 indicate that numbers continue to rise.
The ONS estimates that if all deaths from hanging and poisoning given narrative verdicts by coroners and coded as accidents were, in fact, suicides, the 2009 suicide rate would have been underestimated by 6 per cent - a difference equivalent to almost a third of the National Suicide Prevention Strategy's 20 per cent reduction target.
This may be a conservative assessment because the ONS's analysis did not include all common methods of suicide.
As the number of narrative verdicts rises, so too may the underestimation of suicide, they warn. The consequences of this could be incorrect rate estimates, misleading evaluations of national and local prevention activity, and masking of the effects of the current economic crisis on suicide.
The ONS is currently reviewing its coding of narrative verdicts and the Coroners' Society of England and Wales is investigating how it can improve the current situation.
However, Gunnell and colleagues warn that suicide statistics for the years when narrative verdicts increased "should be treated with caution."
Reliable statistics are crucial to public health surveillance, they say. Changes are needed urgently, but the current Government's proposed abolition of the post of chief coroner "is likely to delay the implementation of recommended improvements and the development of consistent practice across the country."