Shared and distinct alterations in brain connectivity and cognitive function in subthreshold and major depression

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Science

Background:

• Subthreshold depression (StD) is a precursor to major depressive disorder (MDD).
• Understanding StD's neurobiology is crucial for early intervention.
• This study compares neurobiological mechanisms in StD, MDD, and healthy controls (HCs).

Purpose of the Study:

• To investigate the neurobiological underpinnings of StD.
• To compare functional connectivity (FC) and cognitive function in StD versus MDD.
• To identify early neurobiological markers differentiating StD from MDD.

Main Methods:

• Resting-state functional magnetic resonance imaging (fMRI) in 153 StD individuals, 188 MDD patients, and 110 HCs.
• Whole-brain FC analysis using seeds from default mode network (DMN), salience network (SN), executive control network, and affective network (AN).
• Cognitive function assessed across seven domains.

Main Results:

• StD exhibited social cognition deficits; MDD showed multidomain cognitive impairments compared to HCs.
• Both StD and MDD displayed reduced FC between right anterior insula (AI) and left inferior frontal gyrus (IFG).
• Both groups showed increased FC between right subcallosal cingulate and left posterior cingulate cortex (PCC); MDD had additional DMN connectivity alterations.

Conclusions:

• Altered SN and AN connectivity may drive depressive symptoms in StD and MDD.
• DMN alterations might be implicated in the onset of depressive disorders.
• Social cognition deficits in StD are linked to SN connectivity abnormalities.