Ccomments on the original article “Loneliness impairs daytime functioning but not sleep duration,” by L. C. Hawkley, K. J. Preacher, and J. T. Cacioppo (see record 2010-04888-004). The association between daytime dysfunction and loneliness in this article was attributed to nonrestorative sleep caused by loneliness. Loneliness can be divided into two forms: social and emotional, where social indicates a measure of social connectedness or isolation, and emotional indicates a perceived presence or lack of emotional support and closeness (Weiss, 1973). It is possible that the emotional loneliness construct is related to poor sleep quality, rather than social loneliness. Based on the results of their own study, the current authors suggest it is unlikely that the association between loneliness and sleep is due solely to the threat of sleeping alone. Rather, it is proposed that emotional loneliness is the key aspect of loneliness that correlates with sleep quality. (PsycINFO Database Record (c) 2011 APA, all rights reserved)