The P300, loneliness, and depression in older adults.

Depression is associated with high levels of cognitive impairment and increased loneliness among older adults. The current study examines associations between a reliable and robust neural marker of cognitive impairment (i.e., the P300 event-related brain potential [ERP]), loneliness, and depression and assesses the role of loneliness in the P300─depression relationship. In a community sample of 70 older adults between 61 and 75 years, we evaluated cross-sectional associations between depressive symptoms (Geriatric Depression Scale), loneliness (NIH Toolbox), and P300 amplitude measured from the electroencephalogram during a go/no-go task. Results indicated that reduced go and no-go P300 amplitudes were associated with increased depressive symptom severity, with the most unique variance accounted for by a reduced no-go P300 amplitude. Notably, loneliness significantly moderated the no-go P300-depressive symptom severity relationship, such that there was no relationship between the no-go P300 and depressive symptom severity among older adults reporting low levels of loneliness. This finding provides insight into the possibility that social support may offer protection against the depressogenic effects of poor inhibitory control in older adults. Taken together, this study provides a novel examination of the relationships between depression, loneliness, and the P300 ERP in older adults, with important implications for understanding the role of neural inhibition and loneliness in relation to depressive symptomatology.