Two new tests developed by psychologists may one day help doctors predict who is at risk for suicidal behavior, according to two new studies.
The tests aim to objectively measure suicide risk, so rather than directly asking someone if they are thinking about killing themselves, the tests are meant to gauge a person's implicit thoughts and feelings about suicide.
Scores on the tests were associated with both past and future suicide attempts. Importantly, test scores were more accurate than physicians' evaluations in predicting which psychiatric patients would make a suicide attempt in the next six months.
"The fact that both of these different tests improved the prediction of not only who is recently suicidal but who made a suicide attempt in the future suggest that they hold value for improving our ability to predict and hopefully prevent suicide in the future," said study researcher Matthew Nock, a psychology professor at Harvard University.
Prediction problems
Data has long shown that suicide is more common than homicide in the United States. And the rate of suicide is rising, particularly among middle-age people. Suicide is also a leading cause of death globally, with one person dying by suicide somewhere in the world every 40 seconds, according to Nock.
Doctors typically use a patient's self-report of suicidal thoughts to anticipate suicide, Nock said. However, patients often deny or conceal such thoughts, he said.
Another problem is that suicidal thoughts tend to be transient in nature. "A person, when interviewed, may tell the clinician or tell the person asking them that they're not thinking about suicide — they may not be," Nock said. "But those thoughts can return weeks, days, even hours and minutes later."
Also, some patients, including children and those with certain mental disorders, may not be able to clearly communication how they feel or what they will do in the future, Nock said.
For these reasons scientists need to find more objective, nonverbal methods of assessing suicide risk, he said.
"The approaches that psychiatrists and psychologists currently use are fairly straightforward and relatively primitive, I think, to the methods health care professionals use to assess other health risk behaviors and health problems," Nock said. "There's no blood test, there's no X-ray, there's no brain scan that's used to inform risk assessment for suicide."
Objective tests
Some past methods have attempted to find biological markers for suicide, such as abnormal levels of the neurotransmitter serotonin. But these markers tend to be better indicators of personal traits — like violence or impulsiveness — rather than specific behaviors, such as engaging in suicide, Nock said.
Nock and his colleagues developed tests to look for behavioral markers of suicide risk.
The first test is known as the Implicit Association Test and has been used in the past to gauge whether people have implicit race biases.
The researchers modified the test to measure the extent to which patients associated themselves with death.
On a computer screen, subjects saw words related to death (die, dead, deceased, lifeless, suicide), life (alive, survive, live, thrive, breathing), themselves (me, I, myself, my, mine, self), or others (thy, them, their, theirs). One word appeared at a time and subjects were asked to "classify" words to either the right or left side of the screen by hitting one of two keys on a keyboard.
In the first part of the experiment, subjects classified words related to "life" and "self" on one side of the screen and words related to "death" and "others" on the other side. Then the pairs were switched, with "death" and "self" words grouped together.
This test was given to 157 patients at a psychiatric emergency department. Subjects who had attempted suicide in the past were faster at making classifications when the "death" and "self" words were paired than when the "life" and "self" words were paired. People without a history of suicide were faster at making classifications when the "life" and "self" words were paired.
Patients whose scores revealed a strong association between "death" and "self" were six times more likely to attempt suicide in the next six months than patients who had stronger associations between "self" and "life." Physicians' predictions of suicide risk, however, were no better than chance, Nock said.
In the second test, 124 psychiatric patients had to name the color of a word presented on a screen. Previous research has shown when words are particularly meaningful to someone, it takes him or her longer to articulate the color of that word.
Words were either suicide-related (suicide, dead, funeral), general negative words (alone, rejected, stupid) or neutral words (paper, museum, engine).
People who had recently made a suicide attempt paid more attention to the suicide-related words, taking longer to match them with a color, than to the other words. Scores on this test were also better at predicting whether someone would make a suicide attempt in the next six months than physician evaluations.
Future work
While these tests improved upon previous methods for predicting suicide risk, more work needs to be done to enhance their accuracy, Nock said.
Also, patients in the study were not representative of the general population and future studies will be needed to confirm the findings.
Nock hopes the tests, which take about five minutes to complete, might be more widely available outside of psychiatric wards in the future.
The results were published in the August issue of the Journal of Abnormal Psychology and the April issue of Psychological Science.
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