Depression Makes Peripheral Blood Cells More Deformable

Researchers in Germany have studied millions of blood cells from healthy individuals and those suffering from depression and found that cells from the latter exhibit increased deformability. The effect was most pronounced in primary immune cells lymphocytes, monocytes and neutrophils.

Depression affects about 5% of Germans and is marked by loss of interest, joylessness, lack of drive, and increased fatigability. Pathophysiological features of depressive disorders often include low-grade inflammation and elevated glucocorticoid output. But the new study by researchers from the Technische Universität Dresden (TU Dresden), the University of Zurich, and the Max Planck Institutes for the Science of Light and the Max-Planck-Zentrum für Physik und Medizin Erlangen, has established, for the first time, a link between depressive disorders and mechanical changes in blood cells.

The cross-sectional case-control work used image-based morpho-rheological characterization of unmanipulated blood samples facilitated by real-time deformability cytometry (RT-DC).  Sixty-nine pre-screened individuals at high-risk for depressive disorders and 70 matched healthy controls were clinically evaluated by Composite International Diagnostic Interview, a globally recognized clinical interview for psychiatric disorders. Deep learning was then applied to over 16 million blood cell images to classify the main blood cell types as well as morpho-rheological parameters such as cell size and cell deformability.

The researchers found that peripheral blood cells were more deformable in patients with depressive disorders compared to control subjects, while cell size was not affected. Individuals who had suffered from persistent depressive disorder over the course of their lives showed increased cell deformability in monocytes and neutrophils, while erythrocytes were more deformable in current persistent depressive disorder. Also, lymphocytes were more deformable in individuals with a current depressive disorder.

The findings, published in Translational Psychiatry, show for the first time that depressive disorders—and particularly those that persist over a period of more than two years—are associated with increased deformability of blood cells. While all major blood cells tended to show increased deformability, lymphocytes, monocytes and neutrophils are most affected. This suggests that mechanical changes in immune cells occur in depressive disorders, which could be causative for a sustained immune response.

The researchers hope the findings will help contribute to development of more comprehensive depression treatments that combine biological and psychological therapies for more efficient and sustainable results. "We are working in parallel on research into pharmacological therapies to improve a dysfunctional biology as well as psychological therapies to improve dysfunctional cognitive and emotional processes,” says Dr. Andreas Walther, who conducted the study at the Chair of Biopsychology at TU Dresden but is now working at the Institute of Clinical Psychology and Psychotherapy at the University of Zurich. “Indeed, in my opinion, only a holistic approach can understand and efficiently treat this complex disorder and hopefully prevent much suffering in the future."