Synaptic density (SV2A) tracks illness chronicity rather than symptom severity in major depressive disorder

In 34 unmedicated individuals with major depressive disorder, SV2A binding measured by [11C]UCB-J PET shows no association with MADRS symptom severity in dorsolateral prefrontal cortex, anterior cingulate cortex, or hippocampus (r = 0.18–0.26; all p ≥ 0.15).

• Why it matters: Prior work reported an inverse link between depression severity and synaptic density, but replication in an independent PET sample is needed to clarify whether synaptic loss tracks symptoms or illness course.
• What they did: The study analyzed [11C]UCB-J PET data, testing correlations between MADRS scores and SV2A binding in predefined frontolimbic regions, including unadjusted and age/sex-adjusted models, plus models adjusted for episode duration and lifetime episodes.
• The result: After adjusting for duration of the current depressive episode and lifetime depressive episodes, positive associations emerged, and post hoc analyses found longer current episode duration—rather than lifetime depressive episodes—was negatively associated with SV2A binding across primary regions.

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