Someone who develops anorexia is 50 to 60 times more likely to kill themselves than people in the general population. No other group has a suicide rate anywhere near as high (Archives of General Psychiatry, vol 60, p 179).
Recently, psychologists have tried to explain why anorexia and suicide are so intimately connected, something which is helping to answer the wider question of why anyone would commit suicide. If this explanation holds up, it will give psychiatrists a new tool for screening patients and determining which of them are most likely to kill themselves, perhaps saving lives.
Suicide has always been a conundrum for psychologists and other researchers interested in human behaviour. Self-preservation is one of the strongest human instincts, so the drive to commit suicide must be even more powerful. But what causes it?
Suicide is, of course, linked to depression and hopelessness, but nobody has been able to answer the question why some people commit suicide and others, in similar situations, don't. The basic question, and the hopes of understanding the answer through studying anorexia is:
The vast majority of depressed, hopeless people do not commit suicide, so why do some do it?
In 2005, psychologist Thomas Joiner, a suicide specialist at Florida State University in Tallahassee whose own father committed suicide, set out to answer that question. By studying suicide statistics and paying particular attention to the groups with above average rates, Joiner believes he has found a common thread others have missed. "It was the first grand theory of suicide in quite a while," says Nock.
In essence, Joiner proposed that people who kill themselves must meet two sets of conditions on top of feeling depressed and hopeless. First, they must have a serious desire to die. This usually comes about when people feel they are an intolerable burden on others, while also feeling isolated from people who might provide a sense of belonging.
Second, and most important, people who succeed in killing themselves must be capable of doing the deed. This may sound obvious, but until Joiner pointed it out, no one had tried to figure out why some people are able to go through with it when most are not. No matter how seriously you want to die, Joiner says, it is not an easy thing to do. The self-preservation instinct is too strong.
There are two ways people who want to die develop the ability to override the self-preservation instinct, Joiner argues. One is by working up to it. In many cases a first suicide attempt is tentative, with shallow cuts or a mild overdose. It is only after multiple attempts that the actions are fatal.
The other is to become accustomed to painful or scary experiences. Soldiers and police who have been shot at or seen their colleagues injured or killed are known to become inured to the idea of their own death. Both groups also have a higher-than-normal suicide rate. Similarly, doctors and surgeons who witness pain, injury and death are more likely to be able to contemplate it for themselves - the suicide rate for doctors is significantly higher than for the general population. Joiner describes this as a "steeliness" in the face of things that would intimidate most people.