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Perspect Psychol Sci. 2015 Mar;10(2):202-12. doi: 10.1177/1745691614564876.

Loneliness across phylogeny and a call for comparative studies and animal models.

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Center for Cognitive and Social Neuroscience, University of Chicago
Center for Cognitive and Social Neuroscience, University of Chicago Division of Biological Sciences, University of Chicago Pritzker School of Medicine.
David Geffen School of Medicine, University of California, Los Angeles.
Department of Psychology, University of California, Davis.
School Psychology and Child and Adolescent Development, Katholieke Universiteit Leuven.
Biological Psychology Department, VU University Amsterdam.


Loneliness typically refers to the feelings of distress and dysphoria resulting from a discrepancy between a person's desired and achieved levels of social relations, and there is now considerable evidence that loneliness is a risk factor for poor psychological and physical health. Loneliness has traditionally been conceptualized as a uniquely human phenomenon. However, over millions of years of evolution, efficient and manifold neural, hormonal, and molecular mechanisms have evolved for promoting companionship and mutual protection/assistance and for organizing adaptive responses when there is a significant discrepancy between the preferred and realized levels of social connection. We review evidence suggesting that loneliness is not a uniquely human phenomenon, but, instead, as a scientific construct, it represents a generally adaptive predisposition that can be found across phylogeny. Central to this argument is the premise that the brain is the key organ of social connections and processes. Comparative studies and animal models, particularly when integrated with human studies, have much to contribute to the understanding of loneliness and its underlying principles, mechanisms, consequences, and potential treatments.


animal models; loneliness; mechanisms; phylogeny; social neuroscience

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