Suicide kills about 800,000 people every year. Picture: 123RF/Jumlong Choochoui
Suicide kills about 800,000 people every year. Picture: 123RF/Jumlong Choochoui

Suicide poses a mystery to science. How do people manage to get up the nerve to shoot themselves, hang themselves or take a lethal dose of a drug, when doing so violates the strongest instinct that’s been bred into us over millions of years of evolution?

This is not morbid curiosity. The answer could be key to addressing a persistent public health problem: suicide kills about 800,000 people every year, according to the World Health Organisation. In the US, the rate has been climbing over the past two decades.

In his textbook on evolutionary psychology, David Buss of the University of Texas quotes survey results showing suicidal thoughts are correlated with feeling burdensome to others and, especially for men, few prospects to reproduce. For people over 70, suicidal thoughts were correlated with poor health and financial trouble. But there has to be more behind the few who actually attempt suicide, because many people have such problems and feelings and do not try to kill themselves.

In his book Why People Die by Suicide, University of Florida psychologist Thomas Joiner explores the phenomenon from multiple angles: statistics, surveys, case studies, kamikaze pilots, suicide bombers and even forms of self-sacrifice in highly social animals (bees, ants and mole rats). One theme Joiner emphasises is that individuals who die by suicide are fearless. They might be naturally fearless, or they may train themselves to overcome fears.

Voltaire recognised this when writing on the suicide of Roman orator Cato: “It seems rather absurd to say that Cato slew himself through weakness. None but a strong mind can thus surmount the most powerful instinct of nature.”

Joiner’s quest to understand the problem is driven in part by a personal connection to suicide. When he was in graduate school, his father drove off into the night and stabbed himself in the heart. His father, he said, was not a coward.

“People don’t think about this aspect of suicide … but tend to think of it in an abstract way,” he said. When you start to get into the details, it’s pretty clear how difficult it is: the logistics, the fear and pain, the self-preservation instinct.

The US Centers for Disease Control and Prevention recently reported that by career category, suicide is highest among men in construction and mining — physically demanding fields that might require people to get used to injury and face down fears. The rate has been consistently elevated for physicians of both sexes, and they too may be fearless or have learned to overcome fears, making it possible to, for instance, do surgery.

Despair and mental illness are factors too, but there are many people who live with mental illness and the vast majority will not die by suicide. Joiner said the research has revealed a pattern, however. People who die by suicide tend to suffer from what he calls failure of effectiveness: they may have lost a job, or see themselves as career failures. Even more important is thwarted belonging, lack of or loss of close connections to other people.

The evolutionary psychologists have posited that this latter problem poses a suicide risk because of our nature as highly social animals. Joiner has considered this as well. In a 2016 paper published in the journal Psychological Review, he and colleagues looked at self-sacrifice among the world’s most intensely social animals. Some bees will sacrifice themselves by stinging a threatening animal. Naked mole rats will face down a snake, and get killed, to defend their colonies. Ants infected with a contagious fungus will leave a colony and starve rather than risk infecting others.

By saving their colony-mates, even if it means dying, those animals may allow for more of their genes to be propagated. Perhaps human social instincts put our species at risk, especially when people feel they are a burden to their family. As the authors state in the paper, this sort of extreme self-sacrifice, while adaptive in some animals, “represents a tragic, flawed, and sometimes fatal miscalculation (ie a derangement) among modern humans when made and acted upon in the context of suicide.”

In Joiner’s view, those at risk of suicide include a small subset of people suffering from thwarted belonging, failed effectiveness and mental illness, who are also fearless or who have built up a tolerance for fear and self-harm.

Understanding suicide this way doesn’t glorify the act. Nor are lives saved when people who die by suicide are stigmatised as cowards or selfish. Understanding the science of suicide in its starkest terms might help not only identify those at risk but also point to ways to address their suffering.

• Faye Flam is a Bloomberg columnist. She has written for the Economist, the New York Times, the Washington Post, Psychology Today, Science and other publications. She has a degree in geophysics from the California Institute of Technology.

Bloomberg