In 2012, the U.S. Army conducted a workshop to discuss methods to predict the likelihood of soldiers committing suicides. While the high rate of suicides among veterans was the driving force behind the Army’s decision to fund such a program, the idea of predicting someone’s future behavior sounded very Minority Report.
But as researchers from Johns Hopkins University have discovered, it is indeed possible to predict a person’s intent to commit suicide. Not with the help of a “precog,” but by a simple blood test that examines levels of a particular chemical that gets expressed in a single human gene in elevated levels, in response to stress.
"Suicide is a major preventable public health problem, but we have been stymied in our prevention efforts because we have no consistent way to predict those who are at increased risk of killing themselves," said study leader Dr. Zachary Kaminsky, an assistant professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine, in a statement. "With a test like ours, we may be able to stem suicide rates by identifying those people and intervening early enough to head off a catastrophe."
The study is published online in the The American Journal of Psychiatry. It suggests that alterations in the gene SKA2 modifies the way the brain would normally react to stress hormones, and changes what might otherwise be an insignificant reaction to everyday stresses into suicidal thoughts and behaviors.
For the experiment, the team studied the mutation of gene SKA2 in the brain samples of mentally ill patients and healthy individuals. They found significantly depleted levels of SKA2 in samples from people who had died by suicide.
But this was not all. They also found that in certain subjects, this common mutation had undergone an epigenetic modification that altered the way the SKA2 gene functioned without changing the gene's underlying DNA sequence. The modification added chemicals called methyl groups to the gene. Higher levels of these chemicals were found in the brain samples of the study subjects who had killed themselves. The higher levels of methylation among suicide decedents were then replicated in two independent brain cohorts.
A second part of their study involved testing three different sets of blood samples from 325 participants enrolled in the Johns Hopkins Center for Prevention Research Study. The team found similar methylation increases at SKA2 in individuals with suicidal thoughts or attempts.
They then designed a model, which with about 80 percent accuracy could identify participants who were experiencing suicidal thoughts or had attempted suicide. Cases with high risk of suicide were predicted with 90 percent accuracy. In the youngest data set, based on the blood test, the team could predict with 96 percent accuracy, if the subject had suicidal tendencies or not.
The SKA2 gene is expressed in the prefrontal cortex of the brain, the region of the brain last to mature. This part of the brain also dictates if people will be vulnerable to conditions like bipolar disorder, schizophrenia, etc.
SKA2 gene is responsible for regulating the release of stress hormones like cortisol. Any changes to the level or expression of the gene modify the way it channels the stress hormone receptor in to the cells. This results in cortisol being released throughout the brain as the receptor is unable to suppress its release. Previous studies have shown that elevated levels of cortisol affect serotonin, the mood-regulating neurotransmitter, and this imbalance leads to suicidal thoughts.
According to the authors, this simple blood test to help clinicians determine the tendency of a person to commit suicide can be used to devise accurate medical interventions for such people.
It will also help the military to test if soldiers returning from active duty carry the gene mutation, so that suicides can be prevented.
"We have found a gene that we think could be really important for consistently identifying a range of behaviors from suicidal thoughts to attempts to completions," Kaminsky said. "We need to study this in a larger sample, but we believe that we might be able to monitor the blood to identify those at risk of suicide."
Source: Kaminsky ZA, Guintivano J, Brown T, et al. Identification and Replication of a Combined Epigenetic and Genetic Biomarker Predicting Suicide and Suicidal Behaviors. The American Journal of Psychiatry. 2014.