It made the news this past week — researchers have found what they believe to be a blood test that may identify depression in teenagers. But some write-ups of the news got the importance of this possible test completely wrong.
Melissa Healy, writing for the LA Times, for instance, suggested in her opening sentence that, “Even among psychiatric disorders, depression is a difficult disease to diagnose.”
Nothing could be further from the truth. Depression is so easy to diagnose, in fact, that family doctors — who have no special training in psychiatric disorders — feel perfectly qualified to do it every day. You simply ask a person about 9 possible symptoms, and if they agree to 5 or more of them, and have felt that way longer than 2 weeks, they likely have depression.
In fact, it’s so easy to diagnose, we have an online 8 question depression quiz that research has shown can screen for depression nearly as accurately as a professional.
So what’s the real significance of this potential blood test for depression? And what unintended consequences might it have?
The real significance of a blood test that looks for specific genetic biomarkers is that it may identify one form of depression is reducing the prejudice and stigma associated with the disorder. Keeping in mind that such a blood test could only identify the kind of depression that is genetically-passed on from family member to family member, putting future family members at greater risk for being diagnosed with depression.
Being at greater risk doesn’t mean you’re going to get depression, however. Depression remains a complex disorder that is multidimensional. It will always involve psychological, social and biological components. It’s just that in some people, the biological predisposition for depression may be stronger.
Some news stories on this research failed to mention it was a small pilot study involving only 28 subjects. While such research is important, it’s hardly generalizable at this stage of the game.
Other news stories had quotes by experts suggesting a biological marker test such as the one devised by these researchers could lead to more “targeted” forms of treatment for depression. For example, that the genetically-passed form of depression might react better to certain treatments than other forms.
This idea comes from other areas of medicine where, for a tiny set of certain types of diseases that are caused by very specific things, one treatment may be more effective than others. But for depression — where the concern will remain intertwined with other contributing factors — it’s much more of a stretch.
Unintended Consequences of a Genetic Depression Test
So what’s likely to happen in the real world if such a test became widely available? A week or two after your initial diagnosis of depression from a health care professional, some people will get back the results of a blood test that “confirms” the diagnosis.
More importantly, what happens to the second group of people whose lab results come back negative?
Will primary care physicians — the ones who do most of the diagnosing and treatment of depression in the U.S. today — come to view such patients as “faking it” or malingering?
All a genetic biomarker test will really tell us is that some people have a genetically-predisposed form of depression, while others do not. It will not be able to “diagnose” depression itself, because of folks who simply don’t have any genetic markers for depression. And with no specific genetic-focused treatments for depression today, there’s no specialized or targeted form of treatment a person with “genetic” depression would get.
Instead, the unintended consequence of such a test is that some professionals may come to view patients who test negative as not really having a serious form of depression. Or having a type of depression that isn’t as “real” as the kind that people with the genetic biomarkers have.
Last, the researchers actually may not have a test specific to depression (or depression with anxiety). Since they only tested 14 teens who met the current diagnostic criteria for depression, they may actually have created a test more generally for “mental illness.” Until others who have bipolar disorder, pure anxiety, schizophrenia, or other disorders can be tested against these biomarkers, it may be too early to say this test only differentiates depression.
This is an interesting, initial pilot study. It needs to be confirmed with further research, from other scientists, and conducted on much larger and broader populations before we can start getting too excited by it. Until that time, we need to think about what such a test will mean to how depression and other mental illness is viewed, diagnosed and treated in America.
Read the Med Page Today writeup: Biomarkers ID Teen-Onset Depression
Read the LA times article: Blood test looks promising in diagnosing depression