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Definition: loneliness from The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide

Feeling of sadness that results from being solitary and isolated. Loneliness can occur at various stages in life and in different situations. An adolescent in an identity crisis, for example, may be afraid of forming close relationships and be lonely as a result. In the elderly, isolation resulting from degenerative disease, particularly that affecting sight, hearing, or mobility, or due to social factors, such as loss of a spouse or close friends, often leads to loneliness and depression.

Summary Article: Loneliness from Encyclopedia of Human Relationships

The most broadly accepted definition of loneliness is the distress that results from discrepancies between ideal and perceived social relationships. This so-called cognitive discrepancy perspective makes it clear that loneliness is not synonymous with being alone, nor does being with others guarantee protection from feelings of loneliness. Rather, loneliness is the distressing feeling that occurs when one's social relationships are perceived as being less satisfying than what is desired. This entry describes how loneliness is conceived and measured; how loneliness is mentally represented; how loneliness influences thoughts, feelings, and behaviors; and the consequences of loneliness for health and well-being.


Despite general agreement over its definition, loneliness is conceived in a number of ways. One theory of loneliness holds that deficiencies in specific provisions of social relationships contribute to specific types of lonely feelings. For instance, lack of engagement in a social network is associated with feelings of social loneliness such as aimlessness, boredom, and exclusion. In contrast, the absence of a reliable attachment figure (e.g., spouse) is associated with feelings of emotional loneliness, such as anxiety, desolation, and insecurity. More recent studies have shown that these types of lonely feelings are not uniquely associated with certain relationships, however. Marriage, for example, serves a broad social integrative function that diminishes feelings of both social and emotional loneliness, especially for women.

Another theory holds that loneliness arises from social skill deficits and personality traits that impair the formation and maintenance of social relationships. Social skills research has shown that loneliness is associated with more self-focus, poorer partner attention skills, a lack of self-disclosure to friends (especially among females), and less participation in organized groups (especially among males). Personality research has shown that loneliness is associated with shyness, neuroticism, and depressive symptoms, as well as low self-esteem, pessimism, low conscientiousness, and disagree-ableness. Associations among these characteristics have sometimes led to conceptual confusion between loneliness and depressed affect, poor social support, introversion, and/or neuroticism. Research indicates, however, that loneliness, although related, is independent of these characteristics both conceptually and operationally (i.e., the measurement tools for each of these characteristics are relatively specific for the corresponding traits). Moreover, the effects of loneliness on physical health and physiology are generally not explained by the behavioral and personality characteristics with which loneliness is associated, indicating that loneliness may be a unique psychosocial risk factor whose effects are distinguishable from some combination of poor social support, depression, and personality traits.

Loneliness is aversive, but that is not necessarily a bad thing. An evolutionary conceptualization of loneliness holds that the aversive feelings are adaptive because they motivate the repair or replacement of social connections. Human offspring are born to the longest period of near total dependency of any species. Simple reproduction, therefore, is not sufficient to ensure that one's genes make it into the gene pool. For one's genes to make it to the gene pool, these offspring must survive to reproduce. Social connections and the behaviors they engender (e.g., cooperation, altruism, alliances) enhance the survival of the parents; consequently, their children are more likely to survive to reproduce.

In early human history, hunter-gatherers whose genetic predisposition encouraged social/family “togetherness” and the offering of food and protection to mother and child would have increased offspring survival odds, whereas hunter-gatherers who felt no compunction about ignoring social/ family bonds would have reduced the survival odds of their offspring. The latter may have survived to have another family, however, suggesting that no single genetic predisposition is superior. The consequences of such an evolutionary scenario would be heritable individual differences in loneliness, and adoption and twin studies among children and adults support this view. Approximately 48 percent of the variability in loneliness levels can be explained by inherited tendencies to experience loneliness.

The genes underlying loneliness do not act alone. Interactions with the environment bring the expression of an individual's genes to the fore. The genetic biases that account for people's differing sensitivity to the social pain of isolation or rejection, and/or their differing propensity to extract social “nutrients” from the environment, help to determine whether a given social context will dampen or intensify a tendency to feel lonely.

Some social circumstances are fairly uniformly associated with an increased tendency toward loneliness. Marriage is associated with the lowest levels of loneliness; loneliness is greater among those who have experienced divorce and widowhood. Situational factors that influence the availability of social opportunities are also associated with loneliness (e.g., geographic relocation). Social relationship quality is a more potent predictor of loneliness than the existence or quantity of social contacts, however. Relationships that offer security, comfort, trust, and pleasure, even if interactions are relatively infrequent, are much more effective at preventing feelings of loneliness than are more friends or more frequent interactions that fail to meet these standards. Even in marriage, the quality of the relationship determines the degree of protection against loneliness.


Lonely feelings are typically measured using a variety of items that assess the degree to which respondents endorse thoughts and feelings characteristic of loneliness (e.g., “I feel alone,” “I lack companionship,” “I do not feel part of a group of friends”). The result is a continuum in which the intensity and/or frequency of lonely feelings can range from very low (i.e., equivalent to feelings of social connectedness) to very high. On average, lonely feelings are low to moderate in the general population, with only a relatively small percentage of individuals experiencing intense lonely feelings at any given time. When asked simply whether they are currently feeling lonely, approximately 20 percent of the population will respond affirmatively.

Social Cognition
Mental Representations

An axiom in the study of human relationships is that we are highly social animals. A sense of social connectedness is as vital to our survival as food and drink, yet is so taken for granted that only the absence of that sense has been assigned a unique term. This suggests that “not lonely” is the normal or default state required to maintain a healthy and balanced life and that loneliness is the problematic state. Indeed, people's mental representations of their sociality conform to the importance of social bonds at every level of human endeavor.

Studies of loneliness have shown that mental representations of our connections with others are characterized by individual, relational, and collective dimensions. These dimensions correspond to individual, relational, and collective selves posited by theories of the self. At the individual level, feelings of isolation and low self-worth are precluded when people feel comfortable with themselves and their fit in a social world. At the relational level, feelings of interpersonal connectedness are fostered in close dyadic relationships. At the collective level, feelings of group identification and cohesion satisfy a need for belonging. This three-dimensional representation of loneliness holds in young adults and across gender and racial/ethnic lines in middle-age adults, suggesting a universality to this representational structure of the social self.

Mental Processes and Behaviors

Loneliness can be experienced acutely, as a temporary state that resolves when life circumstances resolve (e.g., new friends are made in a new community), and chronically, as a trait-like characteristic that results from an interaction between life circumstances and a genetic bias to experience feelings of isolation. Once loneliness is triggered, it generates a defensive form of thinking—a “lonely” social cognition—that can make every social molehill look like a mountain. Lonely people tend to be more anxious, pessimistic, and fearful of negative evaluation than people who feel good about their social lives, and they are therefore more likely to act and relate to others in ways that are anxious, negative, and self-protective, which leads paradoxically to self-defeating behaviors. For instance, lonely and nonlonely individuals were equally likely to cooperate with a stranger at the outset and during the early trials of a prisoner's dilemma game in which the stranger was playing a tit-for-tat strategy (i.e., cooperation met with cooperation, betrayal with betrayal). This strategy resulted in increased cooperation across trials among non-lonely subjects, but not among lonely subjects. Similarly, self-reports showed that, relative to non-lonely individuals, lonely individuals were less trusting of others and believed that they were less trusted by others. In essence, lonely individuals exercised self-protective behaviors that prevented them from enjoying the positive, cooperative interactions that were theirs to be had.

Not only do the lonely contribute to their own negative reality, but others begin to view them more negatively and begin to act accordingly. One study showed that individuals told that an opposite gender partner they were about to meet was lonely subsequently rated that partner as being less sociable. The individuals primed to have these expectations also behaved toward their partners in a less sociable manner than they did toward partners whom they expected to be nonlonely. Once this negative feedback loop starts rolling, the cycle of defensive behavior and negative social results spins even further downhill. The lonely not only react more intensely to everyday hassles (e.g., misplacing or losing things), they experience less of an uplift from everyday perks (e.g., meeting one's responsibilities) than the nonlonely. In essence, lonely individuals inhabit an inhospitable social orbit that repels others or elicits their negative responses. Even when they succeed in eliciting nurturing support from a friend or loved one, they tend to perceive the exchange as less than fulfilling.

Social rejection is a potent cause of loneliness, and the lonely tend to have a heightened sensitivity to cues of social rejection and acceptance in their environment. For instance, after being presented with autobiographical information (i.e., ostensible diary entries) about a number of individuals, lonely participants remembered a greater proportion of information related to interpersonal or collective social ties than did nonlonely participants. It made no difference whether the detail was emotionally positive or negative. In another study, participants asked to “relive” a rejection experience, a procedure that increases feelings of loneliness, showed greater attention to emotional vocal tone (i.e., a cue for social rejection or acceptance) in a subsequent task than did participants asked to relive more neutral experiences.

Greater attention to social cues does not ensure greater social skills, however. Lonely individuals are less accurate than nonlonely people at decoding facial and postural expressions of emotion, for instance. A lack of correspondence between attention and accuracy in responses to social cues has also been demonstrated in a brain-imaging study of lonely and nonlonely young adults. When presented with equally arousing positive and negative pictures of scenes and objects (nonsocial stimuli) and people (social stimuli), activation in a set of brain regions often associated with visual attention and perspective taking varied in response to negative social (in contrast to matched nonsocial) pictures. Relative to the nonlonely, lonely individuals showed greater visual cortical activation (consistent with greater attention to the negative social than nonsocial pictures) and less activation of the temporo-parietal junction (consistent with less attention devoted to the other person's perspective). Another set of brain regions, associated with reward systems (i.e., ventral striatum), was found to be down-regulated in lonely, compared with nonlonely individuals when viewing positive social (in contrast to matched nonsocial) pictures— results consistent with the idea that lonely individuals derive less pleasure than nonlonely individuals from viewing positive social circumstances. This latter result may bear on the finding that lonely individuals find positive social interactions during the course of a normal day less satisfying than nonlonely individuals.

So although people may become lonely because of a genetic disposition coupled with an unfortunate situation, they remain lonely because of the manner in which they and others think. One might expect that a lonely person, hungry to fulfill unmet social needs, would be accepting of a new acquaintance. However, when confronted with an opportunity to form a social connection, studies show that the lonely are actually far less accepting of potential new friends than are the nonlonely. Similarly, in other studies, lonely students were less responsive to their classmates during class discussions and provided less appropriate and less effective feedback than nonlonely students. Lonely undergraduates also held more negative perceptions of their roommates than did the nonlonely, and this perceptual divide widened as one moved from roommates to suite mates to floor mates to dorm mates.

Time also plays a role in constructing negative “realities.” Researchers asked participants to interact with a friend, and to rate the quality of the relationship and the communication (a) immediately, (b) after watching a videotape of the same social exchange, (c) a few weeks later after being reminded of the interaction, and (d) after again watching the videotape. At all four measurement points, lonely individuals rated relationship quality more negatively than did nonlonely individuals. Interestingly, the further in time they were removed from the social exchange, the more negatively they rated it. Thus, the more time that passed, the more the objective reality succumbed to the “reality” constructed by the lonely individual's negative social cognition.

The Loneliness Continuum Revisited

When loneliness is considered on a continuum that ranges from not at all to very, it is easy to assume that social cognitive and behavioral characteristics differ in degree commensurate with the degree of loneliness. However, individuals who experience few or no feelings of loneliness are characterized by a unique and adaptive profile that is not simply the opposite of the profile of highly lonely individuals. This was evident in a study of three groups of young adults selected from a sample of more than 2,500 undergraduate students to represent loneliness scores in the bottom 20 percent (low loneliness), middle 20 percent (average loneliness), and top 20 percent (high loneliness). Individuals low in loneliness differed from individuals average or high in loneliness on four of five personality dimensions (more outgoing, agreeable, conscientious, and non-neurotic) and scored higher in optimism, positive mood, social skills, self-esteem, and social support and lower in anger, anxiety, shyness, fear of negative evaluation, and negativity. However, individuals average or high in loneliness were indistinguishable on these scales.

These results do not mean that those who are low in loneliness possess characteristics that render them immune to ever feeling lonely. Rather, when individuals feel socially connected, they express a constellation of states and dispositions that enriches their lives not only quantitatively, but also qualitatively relative to individuals who are average or high in loneliness. That is, there seems to be something special about being and feeling socially connected. This interpretation is supported by data from a hypnosis study in which young adults were made to feel lonely and then socially connected (or vice versa, in a counterbalanced order) by recalling a time when they felt rejected and as if they didn't belong, or accepted and as if they did belong. Measures of affect, social factors, and even personality traits mirrored and tracked the acute changes in loneliness induced by the hypnotic manipulation. Participants induced to feel socially connected, compared with lonely, reported significantly less negative mood; higher self-esteem and optimism; better social skills, social support, and sociability; greater extraversion and agreeableness; and less shyness, anxiety, anger, fear of negative evaluation, and neuroticism. This experimental study suggests that loneliness has features of a central trait— central in the sense that it influences how individuals construe themselves and others, and, by extension, how others view and act toward these individuals. Thus, although objective social circumstances (e.g., bereavement, ostracism) can modify feelings of loneliness, subjective social factors operate to keep people in a lonely or socially connected state of being. Whereas lonely individuals think about and behave toward others in a way that tends to reinforce a isolated existence, socially connected individuals hold a more favorable view of others that in turn tends to reinforce their being perceived and treated positively.

Health Consequences

As this profile reveals, when loneliness takes over someone's life, they become trapped in a feedback loop of negative expectations, interpretations, and interactions. The challenge is reframing and redirecting social perceptions so that a sense of meaningful social connectedness can be established or recovered. Fortunately, the same feedback loop that allows individuals to construct a negative, subjective reality can be redirected to construct a better objective reality. This could be particularly important given the health consequences of loneliness.

Loneliness has been associated with alterations in the functioning of the cardiovascular, endocrine, and immune systems. A recent theoretical model of the correlates and consequences of loneliness posits that age-related declines in physiological resilience are accelerated by chronic loneliness. Accordingly, in younger adults, loneliness has been associated with early markers of disease processes (e.g., subtle alterations in blood pressure control mechanisms), whereas in older adults, loneliness has been associated with frank disease (e.g., elevated blood pressure) and dysregulation across multiple physiological systems (e.g., impaired immune functioning and elevated levels of stress hormones). Clearly, the costs of loneliness are too great to ignore.

See also

Attachment Theory, Belonging, Need for, Self-Monitoring and Relationships, Social Isolation, Trust

Further Readings
  • Boomsma, D. I.; Willemsen, G.; Dolan, C. V.; Hawkley, L. C.; Cacioppo, J. T. Genetic and environmental contributions to loneliness in adults: The Netherlands Twin Register Study. Behavior Genetics 35 : 745-752., 2005.
  • Brewer, M. B.; Gardner, W. Who is this “we”? Levels of collective identity and self-representations. Journal of Personality and Social Psychology 71 : 83-93., 1996.
  • Cacioppo, J. T.; Hawkley, L. C.; Ernst, J. M.; Burleson, M. H.; Berntson, G. G.; Nouriani, B.; Spiegel, D. Loneliness within a nomological net: An evolutionary perspective. Journal of Research in Personality 40 : 1054-1085., 2006.
  • Dykstra, P. A.; Fokkema, T. Social and emotional loneliness among divorced and married men and women: Comparing the deficit and cognitive perspectives. Basic and Applied Social Psychology 29 : 1-12., 2007.
  • Epley, N.; Waytz, A.; Cacioppo, J. T. On seeing human: A three-factor theory of anthropomorphism. Psychological Bulletin 114 : 864-886., 2007.
  • Ernst, J. M.; Cacioppo, J. T. Lonely hearts: Psychological perspectives on loneliness. Applied & Preventive Psychology 8 : 1-22., 1998.
  • Gardner, W. L.; Pickett, C. L.; Jeffries, V.; Knowles, M. On the outside looking in: Loneliness and social monitoring. Personality and Social Psychology Bulletin 31 : 1549-1560., 2005.
  • Hawkley, L. C.; Cacioppo, J. T. Aging and loneliness: Downhill quickly? Current Directions in Psychological Science 16 : 187-191., 2007.
  • Peplau, L. A., & Perlman, D. (1982). Perspectives on loneliness. In Peplau, L. A. & Perlman, D.(Eds.), Loneliness: A sourcebook of current theory, research and therapy (pp. 1-20). New York: Wiley.
  • Pinquart, M., & Sörensen, S. (2003). Risk factor for loneliness in adulthood and old age—A meta-analysis. In Shohov, S. P.(Ed.), Advances in psychology research (Vol. 19, pp. 111-143). Hauppauge, NY: Nova Science Publishers.
  • Weiss, R. S. (1973). Loneliness: The experience of emotional and social isolation. Cambridge: MIT Press.
  • Hawkley, Louise C.
    Cacioppo, John T.
    Copyright © 2009 by SAGE Publications, Inc.

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