Blood Test for Depression: A Good Thing?

According to the headline of an article at Scientific American, researchers are making progress in diagnosis of depression by a simple blood test. They celebrate that this may make it possible to treat young adults who are not even aware of their depression. But, as is often the case, the story is not so simple.

First, although between 17-25% of teenagers experience depression, it is unknown whether the cause is genetic, environmental or a combination of the two. In fact, very little is known about depression–and even less is known about how it can be effectively treated. Certainly the evidence in favor of treating depression with selective serotonin reuptake inhibitors (SSRIs) like Prozac, Paxil, Zoloft, Celexa, etc. is limited at best; these drugs have been banned for use in teenagers in some countries because they increase suicide risk. In view of this, the suggestion that it would be helpful to treat teenagers “before symptoms appear,” may be considered more of a threat than a promise (Dr. Sheldon Preskorn, University of Kansas School of Medicine, Witchita).

But, let’s look on the positive side. Since this blood test detects RNA transcripts, it could conceivably detect depression caused by a number of different factors. And, in the best case scenario, it may allow clinicians to distinguish what the cause of the depression is. Of course, this is only if the results reported in the study are reliable, which is by no means certain. After all, the study was preliminary; it was conducted with blood from a very limited number of people and according to Dr. Preskorn, “Anytime you test a number of potential biomarkers on a small group of people you are going to find some biomarkers that look clinically important” (emphasis added). That, of course, does not mean that they are.

So assuming that these positive results are confirmed (and that negative results are published, which is by no means a certainty), would a blood test for depression be helpful? Yes, in that more information is always better. No, in that it might tempt clinicians to take shortcuts and trust the lab results in favor of what the patient reports. Yes, in that it might allow development of more effective treatments for depression. No, in that it might result in teens being given unnecessary medications or drugs that do more harm than good. As always in science and medicine the answers are not that simple. But, acknowledging and considering that fact is what makes good science.