Depression Blood Test: Time For Skepticism

Researchers in Illinois announced yesterday that they have determined a possible biomarker for depression, which could then lead to a possible blood test. The findings were announced in the Journal of Neuroscience, which for some reason doesn't have a copy of the paper or its abstract online. Nonetheless, it's been getting all kinds of news coverage.

"'This test could serve to predict the efficacy of antidepressant therapy quickly, within four to five days, sparing patients the agony of waiting a month or more to find out if they are on the correct therapeutic regimen,' said lead author Mark Rasenick of the University of Illinois at Chicago College of Medicine.

"Rasenick and his colleagues studied the brains of 16 clinically depressed people who committed suicide and compared them to the brains of cadavers with no history of psychiatric disorders.

"They found that a larger proportion of the key signaling protein Gs alpha was trapped in a part of the brain cells called lipid rafts, confirming earlier studies in rats and brain cell cultures.

"'These "rafts" are thick, viscous, almost gluey areas, that either facilitate or impede communication between membrane molecules,' Rasenick said.

"When this protein becomes trapped in the rafts its ability to activate neurotransmitters is reduced.

"'Antidepressants help to move the Gs alpha out of these rafts and facilitate the action of certain neurotransmitters.'"

This is interesting, of course, and there is an obvious need for such a test. But now it's time for a bucket of cold water. Sixteen sample subjects is a very small study and the findings assume that their depression caused their suicides (which might or might not be true), so this is work that will have to be replicated many more times before it can be accepted as sound science. What's more, I cannot find research linking the Gs alphas to depression, so it's possible that they may be a protein several steps removed from the source of depression--a proxy, in short, for a different mechanism behind depression.

So no one should be holding their breaths for this methodology to prove out just yet, nor should they expect a doctor to spring such a test on them anytime soon. As I noted in connection with the recently-announce bipolar biomarker blood test, there are many, many reasons to be leery of the introduction of such tests.

One other curious note: I can find no linkage between Gs alphas and serotonin. So if this biomarker business pans out, what does that mean for ye olde serotonin theory of depression?