Loneliness Definition

Loneliness is defined as the distressing experience that occurs when one’s social relationships are perceived to be less in quantity, and especially in quality, than desired. Being alone and experiencing loneliness are not the same thing. People can be alone without feeling lonely and can feel lonely even when with other people. Loneliness is associated with depressive symptoms, poor social support, neuroticism, and introversion, but loneliness is not synonymous with these psychological characteristics. Loneliness is typically thought of as a stable trait, with individual differences in the set-point for feelings of loneliness about which people fluctuate depending on the specific circumstances in which they find themselves. Loneliness changes very little during adulthood until 75 to 80 years of age when it increases somewhat. Loneliness puts people at risk for mental and physical disease and may contribute to a shortened life span.

History and Theory of Loneliness

LonelinessAlthough loneliness has always been part of human existence, it has a relatively short psychological history. John Bowlby’s attachment theory emphasized the importance of a good attachment bond between the infant and caregiver, and this theory was a forerunner to theories of loneliness. From this perspective, loneliness is the result of insecure attachment patterns that lead children to behave in ways that result in being rejected by their peers. Rejection experiences hinder the development of social skills and increase distrust of other people, thereby fostering ongoing loneliness.

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Attachment theory formed a foundation for an influential psychological theory of loneliness developed by Robert S. Weiss. Weiss identified six functions or needs of social relationships that, if in short supply, contribute to feelings of loneliness. These needs are attachment, social integration, nurturance, reassurance of worth, sense of reliable alliance, and guidance in stressful situations. Weiss went on to distinguish loneliness from social isolation (e.g., a lack of social integration) and loneliness from emotional isolation (e.g., the absence of a reliable attachment figure). As would be predicted by attachment theory, Weiss maintained that friendships complement but do not substitute for a close, intimate relationship with a partner in staving off loneliness. Widows who remarry have been found to escape from loneliness, but those who merely have other friends still feel somewhat lonely about not having a husband.

Another theoretical perspective holds that loneliness is characterized by personality traits that are associated with, and possibly contribute to, harmful interpersonal behavioral patterns. For instance, loneliness is correlated with social anxiety, social inhibition (shyness), sadness, hostility, distrust, and low self-esteem, characteristics that hamper one’s ability to interact in skillful and rewarding ways. Indeed, lonely individuals have been shown to have difficulty forming and maintaining meaningful relationships. They are also less likely to self-disclose to peers, and this helps to explain why they report a lack of intimacy with close friends.

The cognitive approach to loneliness is based on the fact that loneliness is characterized by distinct differences in perceptions and attributions. Lonely individuals tend to look at their world through dark-tinted glasses: They are more negative than are nonlonely individuals about the people, events, and circumstances in their world, and they tend to blame themselves for not being able to achieve satisfactory social relationships. The “perceived discrepancy” definition of loneliness provided previously represents the cognitive perspective. In addition, the cognitive approach largely takes account of the attachment and behavioral perspectives by explaining how (a) failure to meet the need for attachment, social integration, nurturance, and other social needs, results in perceived relationship discrepancies that are experienced as loneliness, and (b) loneliness is perpetuated by way of a self-fulfilling prophecy in which poor social skills result in unsatisfactory personal relationships that, in turn, result in negative self-attributions that lead to further social isolation and relationship dissatisfaction.

Theories of the self have contributed to theories of loneliness by demonstrating the importance of individual, relational, and collective selves. These self-identities correspond to aspects of the experience of loneliness or conversely, the experience of connectedness. For example, at the individual level, if a person’s self-concept expands to include an intimate other (e.g., a marital partner), the person is less likely to experience a sense of isolation than if his or her self-concept fails to include his or her partner. Similarly, a network of close friends and relatives protects against relational loneliness, and group affiliations and memberships protect against collective loneliness.

All these theories of loneliness fit under the umbrella of an evolutionary account of loneliness. According to the evolutionary model, hunter-gatherers who, in times of famine, chose not to return to share their food with mother and child (i.e., did not place a high priority on maintaining social or family bonds) may have survived themselves, but the same genes that allowed them to ignore their family also made it less likely their genes would survive past the child’s generation. In contrast, hunter-gatherers inclined to share food with their family may have lowered their own chances of survival but increased the survival odds of their offspring, thereby propagating their genes. Of course, a hunter-gatherer who survives a famine may then live to have another family another day, suggesting that no single strategy is necessarily best. Such an evolutionary scenario suggests that humans might inherit differing tendencies to experience loneliness. Adoption and twin studies among children and adults have confirmed that loneliness has a sizable heritable component.

Correlates and Consequences of Loneliness

Practically and ethically, loneliness cannot be easily manipulated in an experimental setting. This has posed a challenge to researchers attempting to distinguish between the causes and consequences of loneliness. One creative approach to this obstacle was a paradigm that employed hypnotic suggestion. Using this strategy, highly hypnotizable individuals were asked to relive a time when they felt lonely, and after return from this hypnotic state, to relive a time when they felt highly socially connected. While in these states of social disconnection and connection, participants completed a set of psychosocial measures. The results showed that the states and dispositions that differentiate lonely and nonlonely individuals in everyday life also varied with manipulated feelings of loneliness. That is, when participants were induced to feel lonely, compared with nonlonely, they scored higher, not only on a measure of loneliness, but also in shyness, negative mood, anger, anxiety, and fear of negative evaluation, and lower on measures of social skills, optimism, positive mood, social support, and self-esteem. Conversely, when individuals were induced to feel that their intimate, relational, and collective social needs were being met, they became characterized by states and dispositions that were generally more positive and engaged. This experimental study suggests that loneliness has features of a central trait—central in the sense that loneliness influences how individuals construe themselves and others, as well as how others view and act toward these individuals.

One example of differential construals is that lonely individuals form more negative social impressions and interpret the behavior of others in a more negative light than do nonlonely individuals. Negative social expectations tend to elicit behaviors from others that match these expectations. This reinforces the lonely individual’s expectations and increases the likelihood that the individual will behave in ways that push away the very people who could satisfy his or her social needs. This has been demonstrated in experimental studies in which perceived social threats (e.g., competition, betrayal) cause lonely individuals to respond more quickly and intensely with distrust, hostility, and intolerance.

The negative, self-protective lens through which lonely individuals view their social world also influences how they interpret and cope with stressful circumstances. Lonely individuals are more likely to disengage or withdraw from stressors, whereas non-lonely individuals are more likely to actively cope (e.g., problem solve) and seek tangible and emotional support from others. Passively coping or withdrawing from stressful circumstances is reasonable in certain instances, but when applied generally to everyday hassles, it can lead to an accumulation of stress that becomes increasingly taxing and oppressive. Increased stress may be at least partially responsible for the risk of mental and physical disease in lonely individuals. For instance, loneliness has been associated with elevated levels of stress hormones, poorer immune functioning, and health-jeopardizing changes in cardiovascular functioning.

Individual Differences in Loneliness

Individual differences in loneliness are typically measured using paper-and-pencil questionnaires developed for this purpose. The most frequently used instrument is the UCLA Loneliness Scale, first developed at the University of California at Los Angeles by Daniel Russell and his colleagues. Responses to the 20 items on this scale provide an overall measure of loneliness along a continuum from low to high levels of loneliness. Other loneliness scales have been designed to measure different dimensions of loneliness (e.g., social and emotional loneliness). Some individuals are reluctant or ashamed to report they are lonely, so most loneliness scales avoid using the terms lonely and loneliness.


  1. Cacioppo, J. T., Hawkley, L. C., & Berntson, G. G. (2003). The anatomy of loneliness. Current Directions in Psychological Science, 12, 71-74.
  2. Ernst, J. M., & Cacioppo, J. T. (1999). Lonely hearts: Psychological perspective on loneliness. Applied and Preventive Psychology, 8, 1-22.