Is the salience network larger in people with depression?
Yes. Using repeated, detailed brain scans of the same people, this Nature study found that the frontostriatal salience network occupies nearly twice as much of the cortex in most individuals with depression. The enlargement did not change with mood, and it was already present in children who went on to develop depression in adolescence, so it looks more like a trait that may confer risk than a result of being depressed.
The salience network is a set of brain regions, including parts of the frontal cortex and the striatum, that helps decide what is important to pay attention to, including rewards and emotional signals.
Dr. Kumar’s Take
Most brain imaging in depression has found only modest group differences. This study is different because it used precision functional mapping: scanning the same individuals many times, in some cases up to 62 times over a year and a half, so each person’s own network map could be drawn. The finding that the salience network is enlarged before symptoms start, and stays enlarged whether mood is good or bad, points to a trait-like brain layout that may raise risk. Separately, changes in connectivity within these frontostriatal circuits rose and fell with specific symptoms, which suggests the network map sets the stage while connectivity tracks the mood state.
What the Research Shows
- Nearly twofold expansion: the salience network covered nearly twice as much cortex in most individuals with depression, and this was replicated in several samples
- How it grows: the expansion came mainly from shifts in network borders, with the salience network encroaching on neighbouring networks in three distinct patterns in different people
- Stable over time: the expansion did not change with mood state
- Present before onset: it was detectable in children before depression began later in adolescence
- Symptom tracking: in people scanned repeatedly, connectivity changes in frontostriatal circuits tracked fluctuations in specific symptoms and predicted future anhedonia (loss of pleasure)
Study Snapshot
The researchers used precision functional mapping, which relies on large amounts of resting-state fMRI data from each person, across several samples of deeply sampled individuals with depression and healthy controls, plus a longitudinal sample scanned up to 62 times over 1.5 years.
Why This Matters
If a larger salience network is present before depression starts, it may help identify people at higher risk. The connectivity changes that track symptoms are a separate signal, and they may help explain why depression comes and goes in episodes. None of this has yet been turned into a test or treatment.
Practical Takeaways
- Depression has measurable brain correlates: symptoms like loss of pleasure are linked to specific brain circuits, not character flaws
- The enlarged network did not shrink when mood improved, so recovery does not appear to depend on changing it
- Connectivity within these circuits did track symptoms, which may become a target for future treatments
- This is research, not a clinical test: individual brain maps like these are not part of routine care
Related Studies and Research
Weakened Connectivity Between Salience and Default Mode Networks
Episode 31: Depression Explained, The Biology Behind the Darkness
Episode 32: Depression Recovery Roadmap: A Step-by-Step, Evidence-Based Plan
FAQs
Can brain network changes in depression be reversed?
The size of the salience network did not change with mood state in this study, so it did not appear to shrink when symptoms improved. Connectivity within frontostriatal circuits, on the other hand, rose and fell with specific symptoms.
Do all people with depression show these brain network changes?
No. The expansion was found in most, not all, individuals with depression, and the way the network expanded differed from person to person.
Does depression cause the salience network to expand?
This study suggests not. The expansion was detectable in children before depression began, which points to a trait that may raise risk rather than a consequence of the illness.
Bottom Line
In most people with depression, the brain’s frontostriatal salience network is nearly twice as large as usual. That enlargement is stable, unaffected by mood, and present before depression begins, while connectivity changes within the same circuits track specific symptoms over time.
