Effects of light therapy on amygdala connectivity and serotoninergic system in young adults with subthreshold depression.

BACKGROUND

Bright light therapy (BLT) demonstrates efficacy in alleviating subthreshold depression (StD) among young adults. The amygdala plays a critical role in depression.

METHODS

StD subjects were divided into BLT group (N=47) and placebo group (N=42). Depression severity was assessed using HAM-D, Centre for Epidemiologic Studies Depression Scale (CES-D) and Beck Depression Inventory (BDI) pre-/post-8-week intervention. Structural/resting-state fMRI scan was conducted. Seed-based static FC (sFC) and dynamic FC (dFC) analyses of the bilateral amygdala and their subfields were conducted.

RESULTS

Compared to placebo, BLT showed reduced depression scale, and increased sFC of right basolateral amygdala (BLA)/superficial amygdala (SFA)-right middle temporal gyrus (MTG) and dFC of right centralmedial amygdala (CMA) and right inferior orbital frontal gyrus, and decreased sFC of right amygdalostriatal transition/CMA- left thalamus and dFC of right SFA- right medial prefrontal cortex after intervention; while the whole amygdala and its subnuclei volume did not change significantly after BLT. Right BLA-MTG sFC changes positively correlated with BDI improvement. Baseline amygdala sFC/dFC predicted post-BLT symptom changes. BLT-induced right BLA sFC alterations spatially correlated with 5-HT1A/5-HT2A receptor distributions, and right CMA dFC changes with 5-HT1A.

CONCLUSIONS

Findings suggest BLT modulates amygdala-thalamocortical circuits and serotonergic pathways, highlighting FC biomarkers for treatment efficacy assessment.

TRIAL REGISTRATION CLINICALTRIALS.GOV IDENTIFIER: ChiCTR2000032633.