Depression is associated with dimensional and categorical effects on white matter pathways

Area of Science:

• Neuroimaging
• Psychiatry
• Neuroscience

Background:

• Major depressive disorder (MDD) is associated with reduced fractional anisotropy (FA) in diffusion tensor imaging (DTI) studies.
• The relationship between FA and specific depressive symptoms like anhedonia remains unclear.

Purpose of the Study:

• To investigate the association between FA and anhedonia in adults with MDD.
• To determine if reduced FA in MDD covaries with anhedonia and depressive severity.
• To examine the specificity of these relationships to depression, controlling for anxiety symptoms.

Main Methods:

• Acquired DTI data from 38 unmedicated adults with MDD and 52 healthy controls.
• Extracted DTI metrics from predefined regions of interest.
• Analyzed group differences and correlations between DTI metrics, anhedonia, depressive severity, and anxiety symptoms.

Main Results:

• Reduced FA was observed in the genu of the corpus callosum, anterior limb of the internal capsule (ALIC), cingulum bundle, and uncinate fasciculus (UF) in adults with MDD compared to controls.
• In the MDD group, anhedonia negatively correlated with FA in the genu, cingulum, and UF.
• Anhedonia positively correlated with radial diffusivity (RD) in the genu and ALIC, while depressive severity positively correlated with RD in the ALIC. These findings persisted after controlling for anxiety.

Conclusions:

• Anhedonia is significantly associated with reduced FA and increased RD in white matter pathways crucial for reward processing and value-based decision-making.
• These findings indicate a lawful relationship between anhedonia, a key symptom of MDD, and disruptions in the brain's reward network connectivity.