June 2010


A Biochemical Assay that May Help Predict Adolescent Suicide Risk

Suicide is a leading cause of death among young people. How do you stop it? Currently, the best way is to spot someone at risk and begin counseling, or possibly drug treatment if a psychiatric disorder is involved.

A psychiatric evaluation that someone may be at risk for suicide is complicated and open to interpretation. Complimentary procedures may help rapidly identify those most at risk, and lower suicide rates (save lives).

Damir Janigro (Cleveland Clinic, United States) and coworkers have worked on such an approach. They have developed a biochemical test that, when used in conjunction with psychiatric assessments, may help identify adolescents who are at increased risk for suicide.

Tested patients.

The scientists studied 39 patients admitted to the Cleveland Clinic for treatment of diagnosed psychosis or a mood disorder, and a group of 25 control patients. All of them were from 12 to 18 years old (average age roughly 14 years old).

Patients were excluded from the study if their psychosis was possibly brought about by drug abuse, was the secondary effect of some other medical condition, they were taking lithium (this enhances the effect of some antidepressants), or if they were retarded (IQ less than 70).

Basis of the biochemical assay.

Scientists have previously identified enhanced permeability of the blood-brain barrier in a significant number (over one-sixth) of people who attempt suicide. Testing its integrity may therefore be useful for predicting someone's suicidal tendencies in advance, when used in conjunction with psychiatric assessments.

The blood-brain barrier is a tight packing of cells that separates blood from the cerebrospinal fluid. Currently, the most conclusive methods of determining the integrity of the blood-brain barrier require expensive instrumentation or painful medical procedures; a cheap, non-invasive method would be beneficial.

The scientists tested for the presence of S100B protein in blood serum as an indirect diagnostic of blood-brain barrier integrity. S100B is a protein primarily produced by certain astrocytes (a type of cell in the brain and spinal cord), and is frequently present in large amounts when the nervous system (e.g. the blood-brain barrier) is damaged.

Note that disruption of the blood-brain barrier is implicated in other medical conditions as well, such as multiple sclerosis and epilepsy. Clearly, this test will only be useful as an indicator of suicide risk when it is performed in conjunction with psychiatric assessments.

Testing the biochemical assay.

The scientists divided their patients into two groups. Those people given a score of 1 to 4 were at "low risk" of suicide (thoughts of suicide had either not occurred or had occured no more recently than the past week), and those given a score of 5 to 7 were at "high risk" of suicide (almost daily suicidal thoughts, current suicidal plans, or had attempted suicide within the past week).

They found that risk of suicide risk was positively correlated (statistically significant) with levels of S100B protein in blood serum. This means that the greater the quantitated risk of suicide, the more of the protein the scientists detected.

For example, patients given a suicide risk of 7 had 370 micrograms S100B protein per milliliter of serum. Those given a risk of 1 (and the control patients) had 120 micrograms per milliliter.

Perhaps a more clinically useful result is to compare all those at high risk of suicide to those at low risk. Those deemed to be at high risk of suicide had 2.3 times more S100B protein in blood serum than those at low risk.

Both males and females were equally represented among those at low risk of suicide, but within the high risk group males outnumbered females 2:1. However, the scientists did not uncover a statistically significant effect of gender on the patients' suicide risk score, and no statistically significant effects of body-mass index, height, or weight were found either.

Additionally, nine proteins involved in inflammation were quantitated, and only one of them was significantly correlated with suicide risk. This says that self-induced bodily harm doesn't lead to the elevated S100B protein levels observed by these scientists.

Overall evaluation.

Larg-scale clinical trials need to be performed to conclusively state whether S100B protein levels in blood serum may be indicative of enhanced suicide risk in psychotic adolescents. The biochemical basis of these findings needs more investigation as well.

If confirmed, these findings will help doctors more readily identify patients with a psychiatric disorder who are at more risk of suicide than others. Ultimately, this will enable doctors to provide closer counseling to those most at risk, ultimately helping to prevent suicide and save lives.

ResearchBlogging.org for more information:
Falcone, T., Fazio, V., Lee, C., Simon, B., Franco, K., Marchi, N., & Janigro, D. (2010). Serum S100B: A Potential Biomarker for Suicidality in Adolescents? PLoS ONE, 5 (6) DOI: 10.1371/journal.pone.0011089