The complexity of loneliness Javier Yanguas 1 , Sacramento Pinazo-Henandis 2 , Francisco José Tarazona-Santabalbina 3 1 Scientifc Director of the Elderly Program “la Caixa” Banking Foundation, Spain, President of the Department of Social and Behavioral Sciences at the IAGG-EU; 2 University of Valencia, Spanish Society of Geriatrics and Gerontology, Spain; 3 La Ribera University Hospital, Alzira, Valencia, Spain Summary. Loneliness is a prevalent and global problem for adult populations, and a number of diferent stud- ies have linked it to multiple chronic conditions, including: heart disease, lung disease, cardiovascular disease, hypertension, atherosclerosis, stroke, and metabolic disorders, such as obesity and metabolic disease. Is a major predictor of psychological problems, such as depression, psychological stress, and anxiety. Loneliness is linked to overall morbidity and mortality in adult populations. But limited interventions have demonstrated long-term efectiveness in reducing loneliness in adults with these same chronic conditions. Our research of the extant literature addresses the following question: What evidence exists regarding the relationships between loneliness and health? We focus on recent fndings with respect to the links between loneliness and health. (www.actabiomedica.it) Key words: loneliness, isolation, older people, health, interventions, efectiveness Acta Biomed 2018; Vol. 89, N. 2: 302-314 DOI: 10.23750/abm.v89i2.7404 © Mattioli 1885 Healthy aging - Review Loneliness is a multidimensional and complex construct Tere are more and more elderly people living alone, and some of them are at risk of feeling lonely or socially isolated (1-2), although - as we shall see - lone- liness and isolation are two diferent issues: a person can be alone and not feel alone and vice versa. Weiss (3) afrms that loneliness is a natural phenomenon, a (personal) feeling that may arise at certain moments in life and afect anyone, regardless of gender, age or other socio-demographic characteristics. He also ex- plains that loneliness is often seen as rooted in weak- ness or self-pity, as something that - supposedly - the individual should be able to eliminate, since it is not a physical ailment. Furthermore, he makes the distinc- tion between emotional loneliness and social loneliness. Other authors have defned loneliness from diferent perspectives: as a negative psychological response to a discrepancy between the social relationships one desires (expectations) and the relationships one actually has (objective, real ones); as an individual feeling character- ized by an unpleasant or inadmissible lack of quality in certain social relationships that can occur either because one has fewer social contacts than one wishes to have, or because the level of intimacy hoped for in relationships is not there; as the subjective component of the objec- tive measure of social isolation, in other words, loneli- ness would be the inverse of a situation of social sup- port; as a social pain, something comparable to physical pain, because if physical pain arises to protect us from physical dangers, loneliness would manifest itself as a way to protect us from the danger of remaining isolated (related to the importance of social connections); etc. In general, it is assumed that emotional loneli- ness refers to the absence of an attachment fgure (together with feelings of isolation) and social loneli- ness as the lack of a social network, the absence of a circle of people that allows an individual to develop a sense of belonging, of company, of being part of a community. Both in daily life and in the research area, various researchers have referred to “loneliness” and