New research from the University of Helsinki suggests depression is not a single biological condition but may encompass several distinct brain activity patterns. Using magnetoencephalography on 263 adults with major depressive disorder and 75 healthy controls, the team identified five profiles of functional connectivity—how closely activity in different brain regions is coordinated.
The profiles differed in whether communication between brain regions was stronger or weaker than usual, and in which regions were involved. For example, one group showed the strongest overall connectivity and prominent substance abuse symptoms, while another had widespread weak connectivity and more PTSD-related symptoms. A third group combined unusually strong and weak connections in different areas, with severe depression and lower overall well-being.
The authors note that these contrasting patterns could help explain why previous studies of depression brains have sometimes reached conflicting conclusions, since different patient mixes may show different results. All five groups also differed from healthy participants, indicating that depression involves measurable changes in brain network function—though not a single uniform signature.