Finnish study depression research has identified five distinct patterns of brain activity among people diagnosed with depression, suggesting that the same clinical diagnosis can involve markedly different forms of communication between brain regions.
Researchers at the University of Helsinki examined 263 people with depression alongside 75 healthy participants. By analysing differences in the strength and frequency of functional connections across the brain, the researchers identified five distinct profiles among the participants with depression.
The findings showed that some of these profiles moved in opposite directions. While communication between certain brain regions was stronger than usual in some participants, it was weaker in others, despite all of them having a diagnosis of depression.
“What was particularly interesting was how opposing patterns of brain activity were found within the same depression diagnosis,” said Satu Palva, director at the University of Helsinki’s Neuroscience Center.
Functional connectivity describes how closely different parts of the brain operate at the same time. Researchers use these patterns to examine how different brain regions communicate and coordinate their activity.
The five profiles were also associated with differences in the symptoms reported by participants. One group had moderately strong connectivity and reported a combination of depression, anxiety, excessive worry and reduced functioning.
A second group showed weaker connectivity and generally reported milder symptoms. A third had weak connectivity across a wider area of the brain and showed more symptoms associated with post-traumatic stress.
The fourth profile showed a mixture of weak and strong connections. Participants in this group experienced more severe depression, greater substance use and lower reported wellbeing.
The fifth group had the strongest connectivity of all five profiles. Substance use was more common among these participants, while trauma-related symptoms were less prominent.
All five groups also differed from the healthy comparison group. The differences were not limited to the strength of connections. Researchers also found variations in which areas of the brain were involved and the frequencies at which their activity was coordinated.
The team used magnetoencephalography, or MEG, to record brain activity. The technique measures the magnetic fields generated by electrical activity in the brain and can track changes in neural activity with millisecond precision.
According to Palva, this allowed the researchers to examine the timing of electrical brain activity in greater detail than some methods previously used to investigate possible biological differences in depression.
The findings could help explain why previous research into the biology of depression has sometimes produced conflicting results. If people who receive the same clinical diagnosis can have substantially different, and in some cases opposing, patterns of brain activity, studying them as one group may conceal important biological differences.
The study does not provide a way to determine which treatment should be given to an individual patient based on their brain profile. The researchers describe the findings as a possible direction for future research rather than a clinical method that can currently be used in treatment decisions.
“We are not yet at the point where a brain measurement could be used to select the right treatment for a patient, but the study shows one possible route towards that,” Palva said.
The researchers now aim to develop a clearer understanding of how symptoms, patterns of brain activity and treatment responses are connected. Establishing those relationships could eventually contribute to more individualised approaches to depression, although further research would be required before such brain profiles could be used in routine clinical care.
The scale of depression gives the research broader significance. The World Health Organization estimated in 2025 that about 332 million people worldwide were living with depression, representing 5.7 per cent of adults. In Finland, the University of Helsinki says depression is the most common reason for both long-term sickness absence and disability pensions.
For now, the Helsinki research points to a significant challenge in understanding depression: people can receive the same diagnosis while having very different patterns of activity and communication within the brain. The five profiles do not yet provide a new way to select treatment, but they offer researchers another way to investigate why depression can present differently from one person to another.
