Will a simple blood test diagnose mental illness in the future?

For most folks with mental illness, whether it’s an affective disorder like depression or bipolar or a brain disorder like schizophrenia, identifying and diagnosing the ailment is a subjective process. A diagnosis comes from talking to a therapist, psychiatrist, or physician (or a combination of all three), and sharing your emotions and behavior. But what if you could simply take a blood test and find out if you had a mental illness?

We knew that mental illness could be hereditary, but in a small new study published in the journal EBioMedicine, researchers at the University of California, San Diego think they’ve found a new genetic biomarker linked to mental illness in women.

(Over)express yourself

The researchers analyzed a group of 96 women, 36 of whom were “controls” with no mental illness and 60 of whom had either bipolar disorder or recurrent major depression. In the women with mental illnesses, they found that the expression of genes known as XIST and KDM5C were significantly higher in than the control group.

To confirm their observation, the researchers then obtained 48 RNA samples from postmortem brains of women who had suffered from depression, bipolar disorder, and schizophrenia, as well as controls without mental illness. Once again, they found significantly higher levels of XIST expression in the tissue from bipolar women and a “trend of high level of XIST expression” in the tissue from women with depression compared to the brain tissue of the controls. However, they did not observe a significant difference when it came to KDM5C. (The study did not mention the outcome for women with schizophrenia.)

Great. So what does this finding mean?

For one, it could mean that a simple genetics-based diagnostic test could be used to detect certain mental illnesses—or at least the ability to gauge one’s likelihood of developing mental illness. Early intervention could lead patients or parents to seek out optimal environments for managing diagnoses.

“If our hypothesis is right, if a baby or child has a blood test and shows abnormal [gene expression], our study says that the risk is very high,” lead author and assistant professor of psychiatry Xianjin Zhou told Fusion. “This rarely happens in normal, healthy women. And then you can think about intervention, looking at stress and environment.”

Zhou added that he plans to continue his research with a much bigger sample size—and perhaps most intriguing of all, that it’s only a matter of time before science figures out how to safely and effectively reverse this over-expression.

Correction: An earlier version of this post described the discovery of a genetic marker for mental illness in women as a first, when in fact, other potential markers have been previously identified.