Social support and depressive symptoms: the role of childhood maltreatment and brain activity in a moderated mediation model.

Low social support, characterised by insufficient emotional, instrumental, or informational aid, increases the risk of major depressive disorder (MDD), yet its impact on brain function remains unclear. To examine this, we recruited 32 participants with MDD and low social support, 52 with high social support, and 54 healthy controls. We collected data including functional magnetic resonance imaging measures, sociodemographic information, social support dimensions, depressive symptom severity, and childhood maltreatment to investigate how social support relates to neural activity and depression severity, with childhood maltreatment as a potential moderating factor. Compared to the high social support group, participants with low social support showed decreased fractional amplitude of low-frequency fluctuation (fALFF) in the right superior temporal pole and increased fALFF in the left postcentral gyrus, along with reduced functional connectivity between the right superior temporal pole and right middle occipital gyrus. fALFF in the left postcentral gyrus correlated with physical abuse and inversely with social support. The moderated mediation model indicated that FC between the right superior temporal pole and right middle occipital gyrus mediated the relationship between perceived support and depression severity, with physical abuse moderating this effect. These findings underscore the relationship between social support, brain function, and depression severity.