As a social species, human beings are driven by an innate desire to belong and are thus motivated to develop and maintain meaningful social relationships. As such, perceiving a lack of belongingness strongly impacts psychological and physiological health and well-being. A common form of perceived relationship deficits is loneliness, a negative-affective experience detrimental to health and well-being over time. Through a series of three manuscripts, this dissertation applies the full-cycle model of social psychological research to explore various affective, behavioral, and cognitive consequences of loneliness. Whereas existing models of loneliness focus on long-lasting or chronic forms of loneliness, these studies investigate chronic and transient loneliness, as well as processes through which transient loneliness may develop into more chronic levels. The first paper demonstrates that solitary consumption is a unique behavioral response to transient loneliness, which may exacerbate the experience of loneliness and negatively impact health over time. The second paper provides support for a positivity-deficit perspective, demonstrating that chronic loneliness is related to less disclosure of recent positive experiences, a deficit which may be consequential for the development of close relationships. The third paper demonstrates the role of transient loneliness in inhibiting individuals and their interaction partners from reaping the social rewards of positive-event disclosure, particularly among those who typically feel socially connected. Taken together, these studies expand the current understanding transient loneliness, revealing various social-cognitive and behavioral consequences which could impede the social-reaffiliation process, and thus contribute to the maintenance of loneliness over time.

Current research tends to describe loneliness among the elderly as an individual issue, focusing on psychological or biological causes and negative effects on health. This dissertation lays the groundwork for an alternative, sociological approach. Drawing on the model developed by Durkheim in his study of suicide, the argument operates on three levels. First, it critically examines the dominant analytical framework for studying loneliness, highlighting the influence of concepts and methods inherited from psychology. Next, it contextualizes loneliness historically, tracing through the archives of international organizations (especially the ILO, the WHO, and the Council of Europe) the emergence of policies that contributed to loosening intergenerational ties and isolating the elderly from the rest of society. Finally, the dissertation introduces an innovative quantitative approach based on data from a major European telealarm provider. These "organic" data, derived from real-life settings rather than conventional survey-based research, reveal the macrostructure of the phenomenon. Taken together, the findings point to the need to reconceptualize loneliness not as mere absence of interpersonal connections but as a misalignment of the individual with group norms, especially norms related to time. This has both theoretical and practical implications in terms of the nature of the phenomenon and the types of interventions needed to address it.