Suicide is a sensitive subject, by it’s very nature it seems we are obliged to treat it with kid gloves. In public it is virtually taboo to even mention suicide, in news media euphemisms are employed in order to avoid explicit use of the “S” word. Attitudes are beginning to change, with more vocal discussion about mental illness and euthanasia in both this country and abroad.

One of the key issues is whether a person is capable of deciding to end their own life or if such a decision automatically excludes them from the definition of mentally competent. I found myself pondering these things as I attempted to come up with a way to introduce the research that is ostensibly the focus of this post.

Regardless of your moral position on the subject of suicide I think we can mostly agree that identifying persons at risk of suicidal tendencies would be helpful in alleviating the pain that accompanies this choice (if indeed it can be described as such). This is where a paper published recently in PLoSONE comes in. The study authors point out in the introduction that previous work has been able to correlate increased blood brain barrier permeability with suicide in patients with prior mental disorder.

Perhaps at this point I should take a step back and provide a little more information on what we are discussing here. The blood brain barrier (BBB) is a system of control that restricts what can and cannot pass between the normal circulatory system and the cerebrospinal fluid (CSF) or the bath that your brain sits in.

In practical terms this means tight connections between the cells of your capillaries to prevent leaks and transport systems to get nutrients back and forth across the barrier. Imagine a dam made of tightly packed stones with channels for the controlled movement of water and you have the basic idea.

Anyway, if the BBB becomes more permeable then it is reasonable to suppose that proteins found in the CSF would be found in higher concentrations in the blood than would normally be expected. If the permeability of the BBB is also correlated with suicidal behaviour then the presence of these proteins become an indirect test for suicidal tendencies.

This is the hypothesis that the research then tested, ie. does the presence of proteins in the blood normally found in the CFS correlate with suicidal tendencies? This study looked specifically at a protein known as S100B, primarily associated with certain cells in the brain and spinal cord. Included in the study were 64 adolescents (average age ~14.5 yrs) diagnosed with either psychosis or mood disorders and 20 healthy control subjects.

The subjects were evaluated and their suicidality was ranked from 1-7*, Blood tests then determined the levels of S100B. The findings showed that levels of S100B significantly correlated with suicidality in the subjects. Looking at the data accompanying the study it seems there is a wide margin of uncertainty on these readings. With a relatively small number of subjects I’m not particularly surprised by this but I would be looking to see more investigation into this approach to determine it’s reliability.

Obviously this technique will not replace psychiatric evaluation, it may prove useful though in helping identify those that are most at risk of suicidal behaviour. If I may return to the broader issues I raised at the start of this post, I would also find it interesting if this test (once extensively validated) could separate those who wish to end their lives due to illness into groups consisting of those with suicidal thoughts because of mood disorders and those who are otherwise of sound mind.

Something to think about.

* 1-no suicidality is present, 2-very mild (thoughts when angry), 3-mild (occasional thoughts), 4-moderate (thoughts present in the last week), 5-moderately-severe (recurrent thoughts present almost daily), 6-severe (current suicidal plan), 7-extremely severe (patient attempted suicide within the last week)

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) PMID: 20559426

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