Study: Depression Doesn't Shrink Hippocampus After All — SkimNews
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- Janine Bijsterbosch and colleagues at Washington University School of Medicine in St. Louis analyzed 23,417 brain scans from US and UK participants across six datasets including the UK Biobank, finding no significant link between depression and hippocampal volume.
- The finding directly contradicts a 2015 study of roughly 9,000 people that concluded people with recurrent depression have smaller hippocampi that shrink progressively with each episode.
- The team did link depression to reduced grey matter volume or cortical surface area in the frontal cortex, anterior cingulate, and insula — regions involved in emotional regulation, with the insula possibly vulnerable due to its high neuroplasticity.
- John Fleming of the Southern Colorado TMS Center called the result surprising and said the study shows researchers should not take hippocampal shrinkage as a given.
- Bijsterbosch flagged key limitations: depression was measured at a single time point, and most participants had mild to moderate symptoms, leaving open the possibility that shrinkage occurs in recurrent or severe cases.
- Fleming raised the prospect that brain shrinkage from depression could elevate dementia risk, and noted transcranial magnetic stimulation has been linked to modest volume increases worth exploring as a treatment.
- The findings were published in Nature Mental Health, with Bijsterbosch saying a clearer picture of the brain basis of depression could guide personalized treatment.
Why it matters: The decade-old assumption that depression physically shrinks the hippocampus — long cited as the anatomical basis for its cognitive symptoms — does not hold up in a sample roughly 2.5 times larger than the 2015 study that established it. For researchers and clinicians, the study redirects attention to the frontal cortex, anterior cingulate, and insula as more reliable anatomical correlates, potentially reshaping treatment targets and the long-suspected depression-to-dementia pathway.
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