Summary: Chronic pain and depression often occur together, but many people remain emotionally resilient despite persistent pain. New research identifies how the hippocampus and immune cells in the brain determine whether chronic pain leads to depression.
Researchers mapped a central emotional control region — the hippocampus — and found that depression is not an unavoidable consequence of long-term pain. Instead, a biological tipping point involving neuroinflammation and changes in neural circuits appears to decide who becomes depressed and who stays resilient.
Key Facts & Statistics
- The 20% threshold: Chronic pain affects more than 20% of adults worldwide. Although it is a major risk factor for depression, many people with chronic pain do not develop mood disorders.
- Resilience marker: People with chronic pain who did not develop depression showed a larger hippocampus and increased activity there, suggesting a protective, compensatory brain response.
- Dentate gyrus hub: A subregion called the dentate gyrus — one of the few adult brain areas where new neurons continue to form — acts as a key regulator of stress linked to chronic pain.
- Microglial switch: In resilient individuals, newly generated neurons remain active and buffer stress. In those who become depressed, brain immune cells (microglia) become abnormally activated, causing inflammation that disrupts neuron-to-neuron communication.
- Progressive change: These brain alterations do not appear solely as pre-existing vulnerabilities; they develop progressively in response to prolonged pain.
Source: University of Warwick
Scientists have identified a brain mechanism that helps explain why chronic pain leads to depression in some people but not others, according to a study published in Science.
The results challenge the assumption that depression inevitably follows long-term pain.
Combining large-scale human brain imaging with animal experiments, the investigators found that persistent pain drives stepwise changes in the hippocampus — a region well known for memory and emotional regulation — and that these changes shape whether a person develops depression or remains emotionally resilient.
“Chronic pain often leads to depression or anxiety, but until now we didn’t know why this affects some people and not others,” said co-lead author Professor Jianfeng Feng of the University of Warwick.
“Our work suggests the hippocampus acts as a regulatory center that helps the brain manage emotional responses to ongoing pain. Depression is not predetermined — it depends on how this system adapts over time.”
The brain’s early response to pain
Chronic pain is common — affecting over 20% of adults globally — and is strongly linked with anxiety and depression. Still, many people with persistent pain never develop mood disorders, and the biological reasons for this difference have been unclear.
The researchers analyzed brain scans from large population cohorts, including UK Biobank data, and observed that people with chronic pain but without depression tended to have slightly greater hippocampal volume and higher activity in this region. These structural and functional changes correlated with improved performance on some learning and memory tasks, consistent with an early compensatory response to ongoing pain.
By contrast, people with both chronic pain and depression showed reduced hippocampal volume, altered activity, and poorer cognitive performance. Longitudinal analysis indicated these changes developed gradually as pain persisted.
“The gradual emergence of these alterations suggests they are driven by prolonged pain itself,” Professor Feng explained. “This isn’t solely a pre-existing vulnerability; it’s a dynamic response the brain mounts during ongoing pain.”
From resilience to vulnerability
To clarify how these changes evolve, the team performed parallel studies in animal models of chronic neuropathic pain.
They observed a clear progression of effects: increased pain sensitivity appeared first, followed by anxiety-like behaviors, and later by depression-like symptoms. These behavioral stages coincided with gradual structural and activity changes in the hippocampus, showing how sustained pain can reshape circuits involved in emotional control.
The dentate gyrus emerged as a crucial regulatory hub. Early in chronic pain, new neurons in this area became highly active, indicating an adaptive effort to handle stress. Over time, however, microglia — the brain’s immune cells — became abnormally activated, disrupting normal neuron–microglia signaling and marking a shift from adaptive plasticity to maladaptive circuit remodeling.
When researchers suppressed this abnormal microglial activation in animal models, depression-like behaviors improved while cognitive function remained intact. These results suggest that targeting microglial inflammation in the hippocampus might help prevent depression in people with persistent pain, especially if treatment occurs early.
“This shows the brain is not simply overwhelmed by chronic pain,” Professor Feng said. “It actively tries to regulate emotional wellbeing. If that regulatory system stays balanced, people remain resilient. If it becomes disrupted — particularly by hippocampal inflammation — depression can develop. Understanding this process points to new opportunities for early intervention.”
Key Questions Answered:
A: It is more than a purely emotional reaction — it involves physical changes in brain circuits. The study shows prolonged pain can reshape hippocampal circuitry. Initially the brain attempts to adapt, but continued pain can lead to an overreaction by microglia, flipping a biological “depression switch.”
A: The findings indicate a window of opportunity. Because the transition unfolds progressively, early interventions that reduce microglial inflammation in the hippocampus may help keep the brain in a resilient state even when physical pain persists.
A: Possibly. Resilient patients tended to perform better on learning and memory tests. Since the hippocampus supports both memory and emotion, a stronger hippocampus may better manage chronic pain signals while protecting emotional health.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full.
- Additional context was provided by our staff.
About this depression and pain research news
Author: Matt Higgs
Source: University of Warwick
Contact: Matt Higgs – University of Warwick
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“From chronic pain to depression: Neurogenesis-driven microglial remodeling in the hippocampal dentate gyrus” by Ming Ding, Shitong Xiang, Yuqing Zhang, Lei Wei, Yuanfeng Weng, Xueting Zhang, Yiling Ni, Yuwen Zhang, Qianfeng Wang, Ruiqing Hou, Huaihao Du, Ka Kei Chio, Wei Zhang, He Wang, Tianye Jia, Yi Wu, Jianfeng Feng, Trevor W. Robbins, and Xiao Xiao. DOI: 10.1126/science.aee6177
Abstract
From chronic pain to depression: Neurogenesis-driven microglial remodeling in the hippocampal dentate gyrus
INTRODUCTION
Chronic pain is a major risk factor for depression and anxiety, but the brain processes that translate persistent sensory distress into affective dysfunction are not fully understood. Neuroimaging has implicated the hippocampus in both pain and mood regulation, yet it remains unclear whether hippocampal changes precede, accompany, or result from emotional symptoms. Clarifying this temporal and mechanistic relationship is essential to explain individual vulnerability and to identify intervention points that could prevent the transition to mood disorders.
RATIONALE
The investigators hypothesized that chronic pain triggers a staged remodeling process in the hippocampus rather than a uniform degenerative change. They proposed the dentate gyrus acts as a gatekeeper: persistent nociceptive input is initially handled through adaptive plasticity but can later become diverted into maladaptive circuit destabilization through interactions between adult-born neurons and microglia.
RESULTS
Combining longitudinal human neuroimaging from UK Biobank with rodent models of neuropathic pain, the team identified a conserved biphasic trajectory of hippocampal remodeling. Early in chronic pain, hippocampal volume increased and hippocampal-dependent cognitive performance improved, consistent with adaptive plasticity. As pain continued, this phase shifted to hippocampal atrophy, cognitive decline, and the onset of anxiety- and depression-like behaviors.
At the cellular level, early pain selectively increased activity of newborn neurons in the dentate gyrus and recruited microglia within the neurogenic niche. These cell-type–specific changes progressively heightened local circuit excitability and disrupted network balance, marking the move from adaptive plasticity to maladaptive remodeling. Functionally, different modes of dentate gyrus modulation produced divergent outcomes: suppressing newborn neuron activity reduced affective symptoms but impaired cognition, whereas modulating microglia prevented anxiety- and depression-like behaviors while preserving cognitive function. Together, these patterns identify microglia as central regulators of the pain-to-depression transition.
CONCLUSION
By distinguishing modes of dentate gyrus modulation, the study shows microglia serve as critical and therapeutically accessible regulators of the shift from chronic pain to affective disorders. The transition is not governed simply by hippocampal hyperactivity but by microglia-dependent remodeling that determines whether adaptive plasticity is sustained or diverted into maladaptive circuit states. Targeting microglial activation can preserve hippocampal structure and cognitive function while preventing affective pathology, making microglia a selective leverage point to interrupt progression from chronic pain to mood disorders.