Depression is a slippery condition. Many people are diagnosed as depressed when they're not, and many people suffer without knowing it. Then, there are people who have symptoms that arise from the side-effects of certain drugs and conditions, like thyroid disease.
That's why a simple blood test for depression—or Major Depressive Disorder (MDD) as it's known—could be important. It could one day make depression more like other diseases—a bone fide physiological problem, not something we associate with "feeling blue." That, in turn, could reduce the number of people wrongly given antidepressants (a sort of epidemic in itself).
"It helps the patient to understand their disorder is a medical condition and that it's not their fault," says Lonna Williams, CEO of Ridge Diagnostics, which is developing the test. "It's not just in their head and they can be successfully treated. It gives them an ability to accept their diagnosis and engage with the physician."
A depression test could also help psychiatrists separate people who are genuinely depressed from those who have depressive symptoms from other causes. "It allows the doctor to source the actual cause of those feelings, instead of putting them on antidepressants that will not work in those cases," Williams says.
Ridge, a San Diego-based company, tests blood for nine biomarkers—proteins, hormones and enzymes—that indicate someone with MDD. They run the results through an algorithm, then incorporate factors like gender and body mass index (women with higher BMI are more likely to be depressed, studies show). That produces a number between one and nine. Patients with a score of five and above are 90% likely to have MDD, Williams says.
The test was developed by three scientists with a background in biomarkers and depression. It also came from personal experience. Ridge's chief scientific officer, John Bilello, has a son who was wrongly diagnosed for depression. He was left with a permanent disability from improper treatment.
"This lets doctors begin to prescribe the right drug to the right patient at the right time," says Williams.
The test has been approved by CLIA, the government body that oversees lab procedures. It is now in trials with psychiatrists around the country. Williams says Ridge will probably team up with a bigger company to get the test into clinics. It costs $745 at the moment.
The aim isn't to replace psychiatrists, but rather to give them another tool, she says.
"Many of them see it as assisting them in patient management, particularly in cases when patients have been unsuccessfully treated for quite a long time, and they have a number of other conditions. It makes the patient more aware that it is a real disorder, and that they can be treated for it."