Structural rather than functional brain alterations that characterize the differences between major depressive...

Area of Science:

• Neuroscience
• Psychiatry
• Brain Imaging

Background:

• Major depressive disorder (MDD) and primary insomnia (PI) share symptoms and neurobiological features but are distinct conditions.
• Identifying shared and distinct brain alterations is crucial for understanding MDD and PI mechanisms and improving diagnosis.
• Current research lacks a clear differentiation of structural and functional brain changes between MDD and PI.

Purpose of the Study:

• To identify common and distinct structural (gray matter volume - GMV) and functional (amplitude of low-frequency fluctuations - ALFF) brain alterations in MDD and PI.
• To explore the relationship between demographic/clinical features and these brain alterations using meta-regression.
• To provide insights into the neurobiological underpinnings and diagnostic differentiation of MDD and PI.

Main Methods:

• A systematic literature search was performed across PubMed, Web of Science, and Embase databases up to April 2024.
• Seed-based d-mapping software was utilized to analyze GMV and ALFF abnormalities in MDD and PI compared to healthy controls.
• Meta-regression analysis was conducted to examine the influence of clinical and demographic factors on brain alterations, adhering to PRISMA guidelines.

Main Results:

• Both MDD and PI exhibited increased ALFF in the left temporal pole, superior temporal gyrus (STG), and right amygdala.
• PI showed distinct GMV differences compared to MDD, with smaller volumes in the left striatum and median cingulate/paracingulate gyri (DCG), and larger volumes in the right STG.
• PI displayed lower ALFF in the right cerebellum and parietal regions, but higher ALFF in the right occipital and temporal areas than MDD. Functional alterations were more strongly correlated with symptom severity.

Conclusions:

• Shared increases in resting-state activation within limbic and temporal circuits suggest common neurobiological mechanisms in MDD and PI, potentially representing transdiagnostic phenotypes.
• Distinct patterns of gray matter changes, particularly in the striatum, cingulate, and temporal regions, may serve as biomarkers for differentiating MDD from PI.
• Understanding these shared and distinct neurobiological features is vital for advancing mechanistic insights and diagnostic accuracy for MDD and PI.