Brain Pattern Reveals: Chronic pain has long been known to be associated with depression. Among adults with chronic pain, around 40% exhibit clinical symptoms of depression. But why is it that only some people with chronic pain develop depression?
Researchers have long been wondering why this happens and what goes on in the brain. If we can answer this question, we may be able to prevent depression from developing. Our recent article, published in Science, suggests the answer to this question does indeed lie in the brain. To conduct our study, we analysed neuroimaging brain scans from 14,462 participants from the UK Biobank cohort.
We compared the following groups of participants: people with chronic pain for at least seven years who did not have symptoms of depression, and people with chronic pain who also developed depressive symptoms. For the latter, the depressive symptoms were present either for the entire seven-year period, or they developed after two years or four years. This enabled an analysis of the development of depression associated with chronic pain, using brain imaging.
These neuroimaging analyses revealed something surprising was taking place in the brain – specifically in a structure called the hippocampus. The hippocampus has important functions in learning and memory.
In the participants who reported chronic pain without depressive symptoms, they showed modest increases in hippocampal volume and improved memory performance. This is consistent with the brain attempting to cope with the stress of the pain.
In contrast, people experiencing both chronic pain and depression exhibited reduced hippocampal volume and impaired cognitive performance. Further analyses of these scans suggested these changes developed progressively over time. This indicates that the hippocampus may initially adapt to persistent pain, but it gradually becomes vulnerable when pain continues over long periods.
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Importantly, similar patterns were observed across multiple categories of chronic pain – including back, stomach, knee and hip pain, as well as headaches. This suggests that the findings were not specific to a single type of chronic pain condition.
We then studied how these brain changes unfolded in people with chronic pain by using rodent animal models. This research found that in animals there was a similar sequence of changes in the volume of the hippocampus, accompanied by increased neural activity. Moderate improvements in cognitive functioning occurred initially, but this was then followed by anxiety-like behaviour, which later transitioned to depressive-like symptoms and poorer memory.
Read more: https://www.sciencealert.com/brain-pattern-reveals-why-chronic-pain-leads-to-depression
