HMN 2025: How Blood test identifies biological markers for teen depression and severity

Using a novel lab method they developed, McGill University researchers have identified nine molecules in the blood that were elevated in teens diagnosed with depression. These molecules also predicted how symptoms might progress over time.

The findings of the clinical study could pave the way for earlier detection, before symptoms worsen and become hard to treat. The work is published in the journal Biological Psychiatry Global Open Science.

“Alarmingly, more and more adolescents are being diagnosed with depression, and when it starts early, the effects can be long-lasting and severe,” said senior author Cecilia Flores, James McGill Professor in McGill’s Department of Psychiatry, a researcher at the Douglas Research Center and a principal investigator at the Ludmer Center.

“Teens with depression are more likely to struggle with substance use, social isolation and experience symptoms that often don’t respond well to treatment.”

Notably, the nine molecules—known as microRNAs—have not been linked to adult depression, suggesting they reflect biological processes unique to teens.

A minimally invasive and scalable approach

The study, conducted in collaboration with colleagues at the University of California, Los Angeles and Stanford University, focused on 62 teenagers: 34 with depression and 28 without.

Researchers collected small volumes of blood samples, let them dry, and then froze the samples to preserve molecular integrity over time. Such samples are taken with a simple finger prick and are easy to store and transport, making the approach practical and scalable for broader use.

The McGill team developed the lab method used to extract and analyze microRNAs from the samples.

“Our findings pave the way for using dried blood spots as a practical tool in psychiatric research, allowing us to track early biological changes linked to mental health using a minimally invasive method,” said first author Alice Morgunova, postdoctoral fellow at McGill.

Diagnosing depression mostly relies on self-reported symptoms. The authors say this could delay care, especially if teens don’t recognize the signs or aren’t ready to talk about them. A blood-based screening tool could provide an additional and more objective metric to identify teens at risk.

The researchers plan to validate their findings in larger groups of adolescents and to study how these microRNAs interact with genetic and environmental risk factors.