Study suggests that Pavlovian processes interfere with instrumental learning by promoting action to escape an ongoing aversive stimulus and promoting behavioral inhibition to avoid an impending aversive stimulus.

It is well known that people at high risk for suicide and those who have attempted suicide have certain emotional differences from those people who are not at risk. They are more likely to be depressed, for example. But are there cognitive differences—that is, differences in their thinking styles—as well? This is a question that Matthew Nock at Harvard University has set out to answer in a study that will eventually involve 400 subjects at Harvard and at the Boston VA Medical Center.

Nock’s work has focused on looking for styles of thinking that characterize people who die by suicide. That is, many people are depressed, but only some of them arrive at suicide as a potential solution to that depression. What is it about their styles of thinking that leads them to that conclusion? Previous work has indicated people who attempt suicide pay more attention to the present than to the past or the future; in particular, they seem to have difficulty remembering details of the past or envisioning details about the future. There is also some evidence that suicidal people experience time as passing more slowly. This project is designed to explore those differences more thoroughly.

In one part of the project, which will be conducted at the Boston VA Medical Center, Nock and his team will recruit 100 Veterans who are psychiatric patients at the center because of a recent suicide attempt or because they have been having suicidal thoughts along with 100 Veterans who are at the center for psychiatric care not related to suicide. The goal of this part of the project will be to see if the suicidal Veterans are more likely to be focused on the present at the cost of thinking about the past and the future. “We think people might become hopeless because they’re not able to imaging a positive future,” Nock explains. “The ability to think about the future depends on our ability to remember the past.” Indeed, brain imaging studies show that when people are asked to think about the future, there is activity in the same part of the brain as when they are asked to think about the past. “People recombine pieces of the past when they think about the future,” he says.

In a second part of the project, which will be carried out at Harvard’s psychology department, Nock will recruit 100 Veterans who have been experiencing both depression and suicidal thoughts and another 100 Veterans who have been experiencing depression but not having suicidal thoughts. The goal of this part of the study will be to look at several possible ways that the thinking and mental processes of the suicidal Veterans differ from those of the non-suicidal Veterans. One set of tests will examine time perception, whereas another type of test will look at whether the suicidal Veterans pay increased attention to suicide- and psychological pain-related information. 

In both parts of the study Nock will be looking for consistent differences on the tests and questionnaires between the suicidal and non-suicidal Veterans. He will also follow up at one and three months after the initial tests with phone calls to see which of Veterans has had suicidal thoughts or has attempted suicide since the initial testing. 

A major goal of the research, Nock says, is to overcome the limitations of how clinicians currently evaluate potentially suicidal service member Veterans. Diagnoses now generally rely on self-reports about suicidal thoughts or intents, and the individuals may not always provide accurate self-reports. By developing new, objective ways to measure suicide-related thinking in Veterans, Nock hopes to improve clinicians’ ability to determine which Veterans are most at risk. Furthermore, by understanding differences in how suicidal versus non-suicidal individuals think, Nock said, it may be possible to develop treatments to modify ways of thinking in suicidal individuals in order to reduce their risk of attempting suicide.