Amygdala and hippocampal volumes as neural correlates of resilience and loneliness in older adults.

Loneliness and social isolation increase the risk of physical and mental disorders in older adults, while resilience may mitigate this risk. The evidence that medial temporal lobe (MTL) structures are associated with loneliness, social isolation, and resilience is largely cross-sectional. This study examined whether baseline MTL structures were associated with loneliness, social isolation, or resilience during the COVID-19 pandemic. 114 older adults (59 females; mean age: 73.8 ± 5.6 years) completed magnetic resonance imaging (MRI) before the pandemic (mean interval: 1182.6 ± 559.1 days). They presented with normal cognition (NC; n = 46), mild cognitive impairment (MCI; n = 28), or remitted major depressive disorder (rMDD; n = 40). Amygdala and hippocampal volumes and entorhinal cortex thickness on T1-weighted MRI scans were analyzed using FreeSurfer 7.0. Measures included the UCLA Loneliness Scale (UCLA), the Social Network Index (SNI), the Brief Resilience Scale (BRS), and the Connor-Davidson Resilience Scale (CD-RISC). Linear regressions were adjusted for demographic and clinical covariates. Larger amygdala and hippocampal volumes at baseline were associated with higher resilience (CD-RISC: B = 0.014, p < .001; B = 0.0042, p = .018, respectively). Larger amygdala volumes were associated with lower loneliness (B = -0.013, p = .027), although this finding did not survive correction for multiple comparisons. Sex was associated with loneliness and BRS resilience; females reported greater loneliness and lower resilience than males. Our findings provide hypothesis-generating evidence that amygdala and hippocampal volumes may represent neural correlates of resilience and loneliness in aging that could inform future interventions.