Researchers at the University of Illinois Chicago have identified a biomarker in human platelets that is able to track the extent of depression in individuals.
Published in Molecular Psychiatry, a proof of concept study has built off previous research demonstrating that depression is associated with decreased adenylyl cyclase – an enzyme inside the cell that is made in response to neurotransmitters, such as serotonin and epinephrine.
Lead researcher Professor Mark Rasenick, University of Illinois Chicago, explained the biology of depression: "When you are depressed, adenylyl cyclase is low. The reason adenylyl cyclase is [reduced] is that the intermediary protein that allows the neurotransmitter to make the adenylyl cyclase, Gs alpha, is stuck in a cholesterol-rich matrix of the membrane — a lipid raft – where they don't work very well."
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As a result of identifying that cellular biomarker of the Gs alpha in the lipid rafts, the research team have developed a blood test that can not only indicate the presence of depression but can also suggest a patient's response to therapeutic interventions.
New test could show whether antidepressants are rapidly treating symptoms
Previous studies have shown that when patients taking antidepressants show improved symptoms, the Gs alpha was out of the lipid raft cellular membrane. However, when patients taking medication do not show symptom improvement, the Gs alpha was still stuck in the raft – indicating the antidepressants in the bloodstream was not working.
Currently, patients have to wait several weeks, sometimes months, to determine whether a specific antidepressant has been successful. However, the new blood test, the research team hypothesis, may be able to show whether the antidepressant has been successful after only one week.
"Because platelets turn over in one week, you would see a change in people who were going to get better. You'd be able to see the biomarker that should presage successful treatment," Prof Rasenick said.
Additionally, asides from its potential for treating depression, the ground-breaking test also could assist clinicians better differentiate mental health symptoms from physical health symptoms and improve diagnoses, as Prof Rasenick added: "Most depression is diagnosed in primary care doctor's offices where they don't have sophisticated screening. With this test, a doctor could say, 'Gee, they look like they are depressed, but their blood doesn't tell us they are. So, maybe we need to re-examine this.'"