Japan has one of the highest suicide rates in the world. Indeed, for men aged 20-44 and women between 15 and 34, it is the leading cause of death. The rate equates to about 26 deaths per 100,00 people. By contrast, the rate in the US is just 11 per 100,000.
Which is why the Japanese government has invested heavily in programs to understand the causes of suicide and reduce the number of resulting deaths. Its plan is to cut the rate by 20 per cent by 2017.
Psychologists have studied suicide for many years. One focus of research is identifying and studying people who have regular thoughts about suicide, so-called suicide ideation. The evidence gathered to date suggests that people with suicidal thoughts tend to be socially isolated, meaning they have not just fewer friends but are also less likely to be members of friendship triangles in which three people are mutual friends.
However, these types of studies have been difficult to do accurately. For young people, the data comes largely from questionnaires filled out by students at a particular school or university. The problem here is that when students have friends outside this environment, the outsiders’ role in the social network cannot be properly accounted for.
This doesn’t influence the data for the total number of friends for each person but it may well influence the calculation of the number friendship triangles.
Today, Naoki Masuda at the University of Tokyo in Japan and a couple of pals address this problem. Instead of studying suicide ideation at a school or university, these guys looked at in an online social network called Mixi, a major Japanese network with over 25 million members.