On the World Health Organisation's well-appointed website there is a compendious section devoted to suicide statistics. Among the welter of figures, one chart in particular stands out starkly. It is a simple linear graph showing the rate of suicide worldwide over the past 45 years. The line slopes steeply upwards, demonstrating an increase of 60 per cent over the period. The rate of increase has been steady - the line on the chart is almost straight - and the trend shows no sign of abating. Already the numbers are shockingly high and prompt uncomfortable reflections about what lies behind this contemporary death wish. For the mysterious truth is that while suicide - surely some kind of rough index of human despair - has been increasing, the indices regarding most other measures of human welfare have been steadily improving. Around the world, more people are better housed, better fed and live longer, healthier lives. There is more freedom too - many more millions live in democratic or quasi-democratic societies than did 50 years ago and yet more of us are heading, voluntarily, for the exit door. This is a strange paradox and one that presents an awkward challenge to materialism.

Here is a question: which kills more people worldwide - homicide, suicide or warfare? The surprising truth is that suicide is a much greater killer than the other two. There are now more than one million suicides a year (murders, by contrast, account for about 500,000) and some forecasts estimate this will rise to about 1.5 million by 2020. The number of deaths through warfare is - unsurprisingly - the most variable of the three but most years it doesn't exceed the one million mark. The reality of this suicide epidemic is masked by our own cultural response. Murder and warfare - with all their drama and exciting bloodiness - grab the headlines; suicide, on the other hand, doesn't make for great TV. We generally prefer to turn our gaze away from the bleak reality of self-murder.

The suicide rate varies significantly country by country and region by region, with some countries seeming to suffer a kind of cultural predisposition to suicide with historically high rates. So, for instance, in the Baltic states the suicide rate at around 40 per 100,000, is the highest in the world (by way of comparison the UK rate in 2005 was 6.7 per 100,000), while Russia and many countries previously part of the Soviet Union also fare badly. Japan has its own deeply embedded culture of suicide, which ensures that the country always features near the top of any list of comparative suicide rates. The suicide rate for men nearly always outstrips that for women but the age distribution varies greatly. In some countries, it is the old who are most at risk, in others the middle-aged.