Impaired Interoception Could Be a Predictor of Suicide Risk

Accurately predicting the risk of suicide in an individual is one of the greatest challenges encountered by clinicians. But if there are physical characteristics that differentiate people who have attempted suicide from those who have not, these characteristics could serve as biological indicators of suicide risk. A study published today in eLife found one such characteristic: People who have survived a suicide attempt have higher pain tolerance and are less sensitive to bodily signals related to their heart and breath than people who have not attempted suicide.

“Interoception” describes the way the nervous system tracks the internal state of the body, including our heartbeat, breath, and pain caused by tissue damage. “Unlike most organisms, some humans are able to counteract these survival instincts through the act of suicide,” explains first author Danielle DeVille of the Laureate Institute for Brain Research. “While experts have strived for decades to understand and prevent these deaths, we still don’t know enough about the factors that contribute to suicidal behavior.”

The researchers tested 34 participants with a history of suicide attempts alongside a matched psychiatric reference sample of 68 participants with no history of suicide attempts. They examined interoceptive processing in the participants using a panel of tasks, including a breath-hold challenge, a cold-pressor test, and heartbeat perception. The participants who had attempted suicide tolerated the breath-hold and cold-pressor challenges for significantly longer than those who had not, and they were less able to accurately perceive their heartbeat than non-attempters.

“We found that this ‘interoceptive numbing’ was linked to lower brain activity in the insular cortex, a region that closely tracks the internal state of the body,” explains senior author Sahib Khalsa. “This numbing was not influenced by the presence of a psychiatric disorder, by a history of having considered suicide, or by having taken psychiatric medications, and this suggests it was most closely linked to the act of attempting suicide.”

Khalsa adds that these findings come with a number of limitations, including the fact that the study did not fully examine whether a history of considering suicide, versus making an actual attempt, has an independent impact on interoception. “It is also difficult to judge from our study whether the observed differences in interoception represent innate characteristics of the individuals involved, or whether they reflect an emerging response as they progressed from suicidal thinking to suicidal action,” he says.