HIGH INTELLIGENCE is often associated with the kind of dramatic unhappiness that leads people to suicide. Think Sylvia Plath, Virginia Woolf, Ernest Hemingway, or the notoriously high suicide rates of doctors.
Last month, however, the British Medical Journal published a study that suggested a very different picture. In one of the largest studies on suicide ever conducted, researchers found that men with especially low scores on intelligence tests are two to three times more likely than others to kill themselves.
The study was carried out in Sweden, which, along with other Scandinavian countries, has one of the highest suicide rates in the world. Epidemiologist Finn Rasmussen at the Karolinska Institute in Stockholm and two colleagues monitored nearly 1 million Swedish men, measuring their IQ when they entered national service at 18 and following them until age 44. In that time, 2,811 men committed suicide, with the highest rate found among those who scored lowest on the logical component of the IQ test.
So what does intelligence have to do with suicide? The researchers offer several explanations for their findings. For example, Rasmussen said in a recent interview, a low score might indicate ''difficulty solving problems in a crisis.'' Alternately, he and his colleagues speculated, there may be an indirect link between low intelligence and mental illness. Though recruits known to have depression and schizophrenia (which are often linked to poor performance on IQ tests) were eliminated from some of the analyses, lower IQ scores might indicate a predisposition to developing depression or other mental illnesses later on.
The study also suggested a complicated relationship between IQ, suicide, and education. Men with low IQ scores and only a primary education were no more likely to kill themselves than men with high IQ scores and a higher level of education. But men with low IQ scores and higher education were at a greater risk of suicide. And men with low IQ scores and highly educated parents were at the highest risk of all.
''If you can't live up to the expectations of well-educated parents,'' said Rasmussen, ''it could make you more vulnerable.''
Alan L. Berman, director of the American Association of Suicidology, says that previous work supports the Swedish team's findings. ''There's a lot of research indicating that people who suicide have poorer general problem-solving skills,'' he said. ''They make cognitive errors, they over-generalize or selectively view information. They think much more rigidly.'' But the link between suicide and intelligence per se ''has to be taken with a very large grain of salt,'' he cautions, since ''difficulties with problem-solving could come from almost anywhere-genetics, mental illness, trauma...biochemicals...anything.''
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Still, there's a complex and contradictory body of research on the connection between intelligence and suicide. In 1995 an Australian study on Vietnam era soldiers linked low IQ with suicide. But a 1993 study on Israeli adolescents linked suicide to high intelligence.
Martin Voracek, a psychologist at the University of Vienna, believes that it is people of above-average intelligence who are at greater risk of suicide. For example, he points to two studies showing that suicide is higher for college-educated students and for those identified as gifted. And in a published study of his own, Voracek compared the suicide rates of 85 countries with their average IQ. In general, he found, the higher the average IQ the higher the suicide rate. (Other researchers challenge this sort of cross-cultural research, arguing that both IQ scores and the rate at which suicide is reported are highly influenced by culture.)
As for the Swedish study, Voracek pointed out in an email to the British Medical Journal that a link between high intelligence and suicide could have emerged if the study followed the recruits past the age of 44. In most of the Western world, he points out, the likelihood of suicide increases with age. So most of the suicides in the study group are yet to occur.
But whatever the link between intelligence and suicide, another question remains: What good are these kinds of large-scale epidemiological studies of suicide patterns?
To Berman, there is tremendous value when these studies highlight risk factors for suicide. ''They are not cause-and-effect studies,'' he says. ''But any research which points at significant correlates of suicide alerts clinicians to people at risk ... and helps them intervene accordingly.''
Berman says that the intelligence study is less useful than those that point to risk factors like divorce or unemployment. ''It's not as if I'm going to get more worried about my less intelligent patients versus my more intelligent patients.''
After all, the ''Comprehensive Textbook of Suicidology,'' published in 2000 and coedited by Berman, lists at least 62 independent risk factors for suicide, including mental disorders, alcoholism, substance abuse, social isolation, poor problem-solving, problems with aggression and rage, a sense of worthlessness, and a sense of hopelessness.
Most of these factors stem from beliefs people hold about their lives and the world but-crucially-not from intelligence. ''IQ can't be changed significantly,'' said Thomas Ellis, a psychology professor at Marshall University. ''But with therapy, many of these other risk factors can.''
Christine Kenneally is a frequent contributor to the Globe. Email firstname.lastname@example.org.