A study conducted by researchers at the University of Helsinki has revealed that individuals with the same diagnosis of major depressive disorder may exhibit five distinct patterns of brain activity. This research suggests that the varying symptom combinations in depression may be linked to different neural states.
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Depression can manifest differently among individuals. For instance, some experience heightened anxiety and persistent rumination, while others may face symptoms related to post-traumatic stress disorder (PTSD) or substance abuse. Despite these differences, all can be classified under the same diagnostic label.
The World Health Organization estimates that approximately 332 million adults globally, or around 5.2% of the adult population, are affected by depression. In Finland, it is a leading cause of long-term sickness absences and disability pensions.
To explore the individual variability within the brains of depressed patients, researchers analyzed brain activity in 263 individuals diagnosed with major depressive disorder, comparing their data to 75 healthy control subjects. Utilizing magnetoencephalography (MEG), which measures weak magnetic fields produced by brain electrical activity, researchers were able to capture rapid changes in neural activity.
The study focused on functional connectivity, indicating how closely the activity of different brain regions changes over time. The analysis categorized participants into five groups based on the connectivity strength and frequency between brain regions:
1. **Fairly strong connectivity**: Patients faced severe depression, anxiety, rumination, and reduced functionality.
2. **Weak connectivity**: Symptoms were generally milder compared to other groups.
3. **Widespread weak connectivity**: Individuals exhibited pronounced PTSD symptoms.
4. **A mixture of weak and strong connectivity**: This group experienced greater depression severity, substance abuse, and poor well-being.
5. **Strongest connectivity**: Substance abuse was particularly noted, with less emphasis on traumatic symptoms.
Additionally, all five groups differed significantly from the healthy control subjects in terms of brain region involvement and connectivity frequencies. These contrasting patterns may explain the conflicting findings in previous brain studies on depression, indicating that the same diagnostic category may mask diverse underlying biological changes.
Although MEG allowed researchers to monitor brain activity with millisecond precision—offering insights into immediate brain function—the findings are not yet at a stage where they can guide treatment decisions. Current treatment approaches still rely on clinical evaluations, and patients often undergo various therapies before finding effective solutions.
The study represents progress towards linking specific symptom patterns to brain function. If these connections can be reliably established, brain activity measurements might one day assist healthcare providers in identifying more effective treatments for depression.
This research was published in Nature Mental Health on August 31, 2026.