But all these suicide statistics have to be treated with some circumspection. They are not always reliable and sometimes - as is the case with Africa - do not exist at all. Moreover, there are strong grounds for believing that many countries underestimate the suicide rate. Sometimes this is done deliberately, for transparently political reasons. In 1977, for instance, the German Democratic Republic decided to stop publishing suicide statistics that were becoming an embarrassment for the leadership of the self-proclaimed workers' paradise. In Catholic countries, because of suicide's classification as a mortal sin, the strength of the taboo almost certainly leads to suicides being under-recorded.

British suicide statistics are meticulously kept and are probably among the most reliable in the world, but even so they tell only part of the story. Motivated by compassion for families, coroners often strive to avoid a suicide verdict unless the circumstances leave absolutely no room for doubt. In the recent case of Michael Todd, the chief constable of Greater Manchester, who climbed a mountain in Snowdonia, drank a large quantity of alcohol and took sleeping pills, the coroner recorded a narrative verdict. In an apparent copycat death a few months after Mr Todd's, another policeman, PC Anthony Mulhall, also died on Snowdon after taking sleeping tablets and alcohol. In that case the verdict was death by natural causes.

Having entered all the caveats, though, the suicide statistics remain our only guide to deciphering what is going on here. Statistics may be to truth as paint is to art - which is to say they are raw material requiring creative interpretation - but they must surely be able to tell us something. However, among suicidologists - an ugly construction, but to the point - there is no consensus about the causes of the steadily rising suicide rate.

It was the pioneering French sociologist Emile Durkheim who first gave serious thought to the underlying causes of suicide. In 1897, he published Suicide, one of the seminal works on the subject. By a close analysis of the available statistics, and by his own empirical investigations, he discovered and described rates of suicide among different groups. He found that widowed, single and divorced people were more prone to suicide and that French Protestants were more at risk than French Catholics. He went on to formulate a theory which broadly imagined four categories of suicide: egoistic, altruistic, fatalistic and anomic. Over the succeeding century, the theory was refined and became more sophisticated but Durkheim's taxonomy of suicide has stood the test of time and still provides a useful guide. His crucial insight that a suicide should be seen not only as a unique, individual tragedy, with factors which are sui generis, but also as the outcome of certain forces - cultural, social, religious - acting on that person, is arguably the greatest contribution he made to furthering our understanding.