N. Donovan et al., “Loneliness, Depression and Cognitive Function in Older U. S. Adults,” Geriatric Psychiatry 32, no. 5 (May 2017): 564–73, doi: 10.1002/gps.4495; University of Chicago, “Loneliness Is a Major Health Risk for Older Adults,” ScienceDaily, February 16, 2014, https://www.sciencedaily.com/releases/2014/02/140216151411.htm.
