Loneliness is the distressing subjective experience of perceiving a gap between the social relationships one wants and those one feels one has. It may involve the absence of a trusted confidant, insufficient companionship, a lack of belonging, or the sense of being misunderstood within existing relationships. Its defining feature is perceived disconnection. A person may feel lonely at a crowded gathering and deeply connected during a quiet evening alone. Neither the number of acquaintances nor the frequency of social contact establishes the presence of loneliness. National Academies of Sciences, Engineering, and Medicine (2020); WHO Commission on Social Connection (2025).
Loneliness is an important subject of psychology and public health because it concerns everyday emotional life, the quality of relationships, social participation, and patterns of mental and physical health. Temporary loneliness may follow a move, loss, or disagreement and motivate reconnection. Prolonged loneliness can be accompanied by distress, negative expectations about social encounters, and difficulties sustaining desired relationships. Different pathways may produce similar feelings, so understanding the particular experience matters more than assigning a universal cause. Loneliness is a psychological experience and research construct; it is not an independent psychiatric diagnosis. Qualter et al. (2015).
The World Health Organization's 2025 Commission on Social Connection estimated that approximately one in six people worldwide experience loneliness. This population-level estimate draws on heterogeneous surveys and must be interpreted alongside variation in measures, age groups, cultures, sampling, and thresholds. It describes the scale of the public-health concern while leaving room for considerable differences in individual experience. WHO (2025).
What Is Loneliness in Psychology?
A widely used psychological definition understands loneliness as a perceived discrepancy between desired and experienced social relationships. The discrepancy can concern their number, emotional depth, reliability, reciprocity, or social meaning. Someone who wants one intimate and dependable friendship may feel lonely despite meeting many people, while someone satisfied with a small network may not. The judgment depends partly on personal needs and expectations, which change with age, experience, social roles, and cultural context. National Academies (2020).
Loneliness may be described as longing, sadness, emptiness, exclusion, disconnection, or an inability to share what matters. These descriptions point toward overlapping experiences rather than a mandatory symptom list. People can feel lonely occasionally or persistently, and severity may change from one social setting to another. A single moment of solitude, a modest friend group, or a desire for privacy provides too little information to establish distress.
Emotional and social dimensions
An emotional dimension involves the perceived absence of a close, dependable bond. A social dimension involves feeling insufficiently connected to a wider group, network, or community. Both may occur together. Someone with a trusted partner may miss friends and community membership, while someone with an active network may lack a person with whom they can be emotionally open. These distinctions clarify what kind of connection is desired, although the real experience of loneliness often crosses conceptual boundaries.
Different relationships serve different functions. Close friendship may provide shared vulnerability and a sense of being known; a community may provide participation and recognition; casual, familiar encounters may contribute everyday belonging. Research on adult friendship finds that friendship quality and social participation are associated with well-being, while noting gaps in causal evidence and diversity across study designs. The meaningfulness of a bond therefore matters alongside network size. Pezirkianidis et al. (2023).
Loneliness as a social signal
A prominent theoretical account proposes that perceived social disconnection can activate a motive to restore connection. Qualter and colleagues described a reaffiliation motive across the lifespan: loneliness may encourage social approach, but reconnection can become difficult when expectations of rejection, environmental barriers, or changing developmental circumstances interfere. This model organizes evidence about social motivation; it does not imply that every lonely person behaves identically or that all episodes have the same origin. Qualter et al. (2015).
Loneliness Compared With Related Concepts
Social isolation
Social isolation refers to objectively limited social contact or network integration. Loneliness concerns subjective experience. A person living alone with relatively few contacts can feel socially fulfilled; a person surrounded by colleagues, relatives, or online acquaintances can feel painfully disconnected. Living arrangements, the size of a network, and the frequency of meetings cannot substitute for questions about perceived connection. The distinction is fundamental to accurate research and individual assessment. National Academies (2020).
Social isolation can create obstacles to assistance and participation even when loneliness is not reported. Conversely, reducing the number of objectively isolated days does not guarantee that a person will feel more understood. An appropriate response identifies whether the primary difficulty concerns access to others, meaningful relationship quality, or both.
Solitude
Solitude means time spent apart from other people and can be deliberately chosen for reflection, rest, creative work, autonomy, or enjoyment. Its meaning depends on preference and circumstances. Time alone can be restorative when chosen and distressing when imposed or prolonged beyond a person's wishes. The capacity to reconnect when desired often matters. A preference for quiet or a small number of friends should be understood within the individual's own needs.
Belonging and social support
Belonging refers to experienced inclusion, acceptance, and meaningful membership in relationships or communities. Social support describes resources associated with social ties, including emotional care, practical assistance, information, and perceived availability of help. These constructs overlap with loneliness but differ in what they assess. Someone can receive practical assistance while feeling emotionally unseen, or feel a strong sense of belonging without frequent direct help.
The specialized stress-buffering function of social support is explored in Social Support and Stress: When Relationships Buffer Strain. Here the central question is whether the person's relationships meet desired needs for connection, recognition, and reciprocity.
Why Do People Feel Lonely? Main Causes and Risk Factors
Loneliness develops through interactions among relationship changes, expectations, available opportunities, physical health, social settings, and psychological processes. Research identifies conditions associated with loneliness; most cannot be treated as isolated sufficient causes. The WHO Commission emphasizes the combined influence of individual circumstances and structural conditions, including income, discrimination, disability, and access to social participation. WHO (2025).
Separation, bereavement, and disrupted routines
The end of a relationship, death of a loved one, relocation, migration, graduation, job change, or retirement can interrupt a network of familiar interactions. Even welcome transitions may remove routine encounters that previously gave life continuity. A person may miss shared history, recognition, practical cooperation, or a particular kind of emotional intimacy. The resulting loneliness can be a comprehensible response to changed circumstances rather than evidence of personal inadequacy.
A major transition can also alter identity. Someone may miss being a teammate, colleague, close neighbor, or participant in a familiar community. Rebuilding connection can require repeated encounters over time, during which new relationships gradually acquire shared meaning. A fuller account of intimacy loss and changing networks is available in Loneliness After a Breakup.
Lack of intimacy within existing relationships
Frequent conversation, shared residence, or numerous contacts can coexist with loneliness when interactions lack trust, emotional safety, mutual attention, or responsiveness. A person may hesitate to express concerns, expect dismissal, or experience consistently one-sided contact. The relevant problem may be relationship quality rather than the sheer quantity of interaction. The review by Pezirkianidis and colleagues links adult friendship characteristics with well-being, while the observational nature of much of this literature limits conclusions about causation. Pezirkianidis et al. (2023).
Emotional disconnection within marriage has its own relational mechanisms and canonical article, Loneliness in Marriage: Why You Can Feel Alone With Your Spouse. The broader principle is that physical proximity and experienced intimacy are separate dimensions.
Exclusion and limited access to connection
Discrimination, poverty, inaccessible buildings, limited transport, unsafe neighborhoods, unstable housing, language barriers, demanding work schedules, and caregiving responsibilities may make participation difficult. People facing these barriers can have a strong desire for connection while lacking realistic opportunities to develop it. An explanation based only on social skills would overlook external conditions. Public-health approaches therefore consider practical access and community environments alongside psychological factors. National Academies (2020); WHO (2025).
Libraries, classes, volunteering, community organizations, and familiar public settings can support repeated encounters, but their value depends on whether they are accessible, welcoming, affordable, and appropriate to the individual. The specialized evidence concerning cafes as social spaces belongs to Coffee Shops and Loneliness.
Chronic illness and physical limitations
Pain, disability, fatigue, sensory impairments, and reduced mobility may complicate social interaction and change the ways people maintain relationships. Illness may reduce access to shared activities; social distress can also coexist with patterns of sleep or behavior relevant to health. These connections can operate in both directions, making simple causal narratives unreliable. Practical accommodations and flexible modes of interaction may matter as much as motivation. National Academies (2020).
Differences in social needs and expectations
People differ in preferred levels of interaction, emotional intimacy, disclosure, and independence. Some seek a broad social network; others want only a few highly reciprocal relationships. Expectations are influenced by family experiences, developmental changes, cultural practices, and the reliability of past connections. A person whose preferred form of companionship is unavailable may feel lonely even when socially active. Assessment should therefore ask which relationships are meaningful and what is missing, rather than prescribing a universal ideal number of friends.
Psychological Mechanisms That Can Sustain Loneliness
Vigilance for rejection and social threat
Hawkley and Cacioppo proposed that perceived isolation can heighten vigilance for potential social threat. Ambiguous behavior may then be interpreted pessimistically: a delayed message seems like rejection, a distracted face appears unfriendly, or a missed invitation feels like evidence of exclusion. Such interpretations may encourage caution and make interactions less rewarding. The model is supported by theoretical and empirical work but should not be universalized; real rejection, discrimination, or relational unreliability can also explain negative expectations. Hawkley and Cacioppo (2010).
Attention, memory, and expectation can reinforce one another. Someone who remembers painful encounters vividly may approach new relationships with uncertainty, disclose less, and find it difficult to test whether others are trustworthy. Reduced opportunities for positive experiences can then maintain distress. This account describes a possible feedback process, not an inherent personality defect or a single explanation for every person's loneliness.
Wanting connection while withdrawing
Loneliness can generate a desire to reconnect while disappointment or anxiety makes social approach difficult. A person may decline invitations because they expect exclusion, remain guarded in conversation, or withdraw after ambiguous interactions. Qualter and colleagues emphasize that the reaffiliation motive can be interrupted by psychological and contextual factors across development. Responses also differ: some people actively reach out, invest more in familiar relationships, or seek lower-pressure communities. Qualter et al. (2015).
Self-appraisal, shame, and trust
Loneliness may be accompanied by self-criticism or the belief that being disconnected reveals personal inadequacy. Shame can make the experience difficult to discuss and may interfere with seeking support. These feelings should be understood in their actual context. Someone who has experienced repeated exclusion may have well-founded concerns about the environment, while another person may benefit from examining interpretations of ambiguous behavior. Support can address both expectations and the need for safer, more reliable relationships.
Stress and sleep-related processes
Psychobiological models connect persistent perceived isolation with heightened arousal, sleep disturbance, and stress-related functioning. Hawkley and Cacioppo reviewed evidence for the interplay of social vigilance, sleep quality, psychological responses, and health behavior. Many studies are observational and involve reciprocal relationships or other influences. Biological plausibility alone does not determine how much of a particular health outcome is caused by loneliness. Hawkley and Cacioppo (2010).
Psychological Effects of Loneliness
Sadness, emptiness, and diminished well-being
Loneliness can produce sadness, longing, frustration, emotional exhaustion, or a feeling that important experiences remain unshared. Some people describe a persistent sense of distance from others even while participating in ordinary life. Severity varies by circumstance and individual. Psychological studies link loneliness with poorer self-reported well-being, but this relationship reflects a complex pattern involving health, financial circumstances, relationship quality, and previous distress. Personal experience should be explored rather than inferred from a survey score alone.
Depressive symptoms and depressed mood
Loneliness and depression are related concepts with separate definitions. Loneliness refers to inadequate perceived social connection; depression concerns a broader set of changes in mood, interest, energy, cognition, sleep, and functioning, and a depressive disorder requires clinical criteria. A meta-analysis of 37 studies by Chen and colleagues found evidence of reciprocal longitudinal prediction between loneliness and depressive symptoms. Earlier loneliness predicted later depressive symptoms, and earlier symptoms also predicted later loneliness. Predictive associations remain distinct from proof of direct, universal causation. Chen et al. (2023).
The reciprocal pattern matters because low energy, withdrawal, and negative self-appraisal can make social engagement harder, while unmet relational needs may deepen distress. Interventions targeting connection cannot automatically replace assessment and care for a depressive disorder. Equally, a person can report loneliness while having no diagnosable psychiatric condition.
Anxiety and anticipation of rejection
Loneliness may coexist with worry about being evaluated, memories of exclusion, or uncertainty about initiating conversation. These experiences can reinforce each other without being identical. Social anxiety has its own diagnostic features and treatment evidence, while some lonely individuals are socially confident and experience disconnection for other reasons. The practical question is whether fear, context, or relationship dynamics are obstructing desired connection.
Trust, self-esteem, and relationship expectations
Repeated experiences of exclusion may influence perceived social value and trust in future encounters. A person may become convinced that others will not understand them or that relationships are unlikely to last. Such beliefs may reflect personal history, current emotional distress, actual relational conditions, or several factors together. The link between negative affectivity and loneliness is addressed more specifically in Neuroticism and Loneliness; a personality trait should never be assumed to explain everyone's circumstances.
Attention, rumination, and daily functioning
Persistent interpersonal distress may compete with attention needed for study, work, or leisure. Some people spend substantial time revisiting conversations, anticipating rejection, or waiting for replies; others reduce participation because repeated attempts to connect feel unrewarding. These experiences can impair well-being without constituting a universal cognitive syndrome. Marked changes in concentration or functioning call for consideration of sleep, depression, anxiety, medical conditions, and social pressures.
Suicidal distress and clinical safety
Severe loneliness may coexist with hopelessness or suicidal thinking, although loneliness by itself is not a suicide prediction or diagnostic category. If someone describes imminent intent to self-harm, an inability to remain safe, or an immediate danger, urgent safety assessment and contact with local emergency or crisis services take priority over ordinary relationship advice. Persistent loneliness accompanied by significant impairment deserves appropriate professional attention even in the absence of an emergency.
Physical Health Associations and Causal Limits
Research links loneliness and social isolation with multiple health outcomes, yet associations can reflect reciprocal causation, confounding, selection, or shared risk factors. Longitudinal studies establish temporal sequences more clearly than cross-sectional studies; they do not automatically identify an intervention effect. Population averages cannot determine an individual person's prognosis. It is essential to examine which social construct a study measured and whether its results concern association, prediction, biological pathways, or randomized intervention evidence. National Academies (2020).
Mortality and cardiovascular outcomes
Wang and colleagues reviewed 90 prospective cohort studies comprising more than 2.2 million adults. Their pooled general-population estimates associated social isolation with all-cause mortality at 1.32 and loneliness at 1.14. The differing magnitudes reflect different exposures and analyses. These values are observational relative association estimates, not experimental proof that reducing a particular person's loneliness will lower their death risk by a corresponding amount. Cardiovascular and cancer outcomes also varied according to the exposure and analytic subgroup. Wang et al. (2023).
Possible pathways include stress-related physiology, sleep quality, access to practical care, and health behaviors. Those mechanisms are scientifically plausible and worthy of investigation but do not remove the influence of underlying medical conditions, material circumstances, or reverse causality. Clinical prevention should evaluate established medical risks alongside social conditions.
Cognitive impairment and dementia
Luchetti and colleagues' 2024 meta-analysis combined longitudinal aging data and published research. Its dementia analyses included 21 samples comprising more than 608,000 participants and found an association between loneliness and later dementia outcomes, including after adjustment for some relevant covariates. Heterogeneity in loneliness measures, ascertainment of dementia, and remaining confounding complicate causal interpretation. These findings support additional research; they do not establish that a loneliness-reduction intervention prevents dementia. Luchetti et al. (2024).
How Psychologists and Researchers Measure Loneliness
Loneliness is typically assessed through self-report questions describing feelings of disconnection or relational adequacy. Russell's UCLA Loneliness Scale (Version 3) is a widely studied instrument. Its validation included reliability and construct-validity analyses across several samples. Researchers use such measures to compare patterns and evaluate outcomes; the results depend on question wording, recall periods, culture, and population. A loneliness scale is not a test that diagnoses a psychiatric disorder. Russell (1996).
Other measures examine emotional and social dimensions separately. Brief single-item questions can be useful in large surveys but cannot provide the same descriptive detail as a fuller interview. Estimates of prevalence may differ because researchers use different questionnaires, thresholds, and time frames. A decline in an intervention study's loneliness score also does not establish that the participant developed durable reciprocal friendships.
Individual assessment adds context to measurement. Useful questions concern what kind of connection is missing, which relationships matter, whether changes followed a life event, and whether access, safety, health, or past experiences are shaping the situation. These questions allow similar scores to represent very different circumstances and potential supports.
Loneliness Across the Lifespan
Children and adolescents
Young people's relationships develop alongside family life, peer acceptance, school belonging, and changing identity. School transitions, exclusion, bullying, and difficulties finding trustworthy friends may shape experiences of loneliness. Developmental accounts recognize that the motivation to reconnect changes across childhood and adolescence. A distressing experience must be understood against the child's actual environment, rather than treating ordinary differences in sociability as pathology. Qualter et al. (2015).
Early and middle adulthood
Leaving education, relocating for employment, parenting, caregiving, financial pressure, and changes in friendships can alter the time and opportunities available for meaningful connection. A full schedule may coexist with loneliness when it contains few interactions that feel reciprocal or personally significant. Familiar routines and accessible shared activities can help relationships develop, but the fit with individual responsibilities and needs is crucial.
Older adulthood
Bereavement, retirement, sensory difficulties, changing mobility, and shrinking access to familiar settings may contribute to loneliness in later life. Aging itself is not a sufficient cause: many older adults maintain strong relationships and satisfying community participation. The National Academies report emphasizes the importance of practical risk factors and the distinction between subjective loneliness and objective isolation. The dedicated article Loneliness and Social Isolation in Older Adults examines these questions in depth. National Academies (2020).
Culture, migration, and social inequalities
Norms concerning intimacy, family contact, reciprocity, privacy, and social obligations differ among communities. Migration may interrupt familiar roles, language-based belonging, and everyday contact while preserving valued long-distance relationships. Marginalization can reduce safe opportunities for participation, and economic pressures may restrict time or resources for connection. The WHO report supports attention to such structural conditions while recognizing the limitations of comparing prevalence across different survey methods. WHO (2025).
How Can Loneliness Be Addressed?
A constructive response begins with the specific unmet relational need. Someone lacking a dependable confidant faces a different challenge from someone needing accessible transport, safer community spaces, relief from a distressing relationship, or help with severe depressive symptoms. A useful plan may combine meaningful contact, better opportunities for participation, attention to relationship quality, and professional support when indicated.
Deepen reliable, reciprocal relationships
Existing relationships may offer opportunities for more consistent and meaningful connection. Initiating a shared activity, expressing a concrete need for companionship, or rebuilding contact with someone trusted can help when both people welcome the exchange. The aim is sustainable mutual recognition, not compliance with an arbitrary target number of messages or encounters. Relationships characterized by coercion, mistreatment, or chronic invalidation call for safety and appropriate boundaries.
Make recurring social opportunities accessible
Friendships often develop through repeated interactions rather than a single successful social event. Classes, volunteering, neighborhood activities, community organizations, or interest-based groups can provide continuity. The accessibility, affordability, shared interests, and social climate of the setting matter. For people with disability, caregiving responsibilities, geographic isolation, or limited transportation, remote or small-group formats may offer realistic forms of participation.
Work with interpretations and social expectations
When anticipation of rejection becomes a barrier, reflection on ambiguous social cues and gradual, manageable approaches to contact may be useful. Psychological work should distinguish assumptions that can be examined from experiences of actual mistreatment. Interventions focused on maladaptive social cognition have a research history, but their effectiveness varies by design and population. Masi et al. (2011).
What intervention research establishes
A preregistered systematic review by Lasgaard and colleagues identified 312 intervention studies and included 280 in its meta-analysis. Randomized controlled trials showed an average short-term improvement in loneliness, while the authors graded confidence in effect estimates as low or very low. Psychological interventions appeared comparatively promising, yet which approaches work best for specific groups and how consistently benefits persist remain open research questions. Published online in October 2025, the paper appeared in a 2026 issue of American Psychologist. Lasgaard et al. (2026).
An earlier meta-analysis by Masi and colleagues organized interventions into strategies addressing social skills, social support, opportunities for social contact, and unhelpful social cognition. These are useful mechanisms for intervention design rather than a uniform menu of proven cures. Small samples, different comparison conditions, self-report outcomes, variable follow-up, and population differences require care when interpreting efficacy. Masi et al. (2011).
When clinical or practical help is needed
Professional evaluation can be valuable when loneliness is persistent and severe, interferes substantially with functioning, follows trauma, or accompanies significant mood, anxiety, sleep, or safety concerns. Appropriate care may address co-occurring psychiatric symptoms or interpersonal difficulties, while social services and community supports can address access and material barriers. Psychological treatment and practical opportunities for social participation respond to different, sometimes complementary needs.
Digital Relationships and the Artificial Era
Online friendship, social networking platforms, moderated communities, conversational AI companions, and clinical digital interventions involve distinct forms of interaction and different evidence bases. Digital connections may sustain valued friendships across distance or provide accessible participation when in-person opportunities are limited. They can also involve comparison, exclusion, or interactions that fail to satisfy desired intimacy. The separate canonical research article Social Media and Loneliness examines platform-specific evidence and individual differences.
An AI companion may provide conversational availability and short-term perceived support, while its longer-term relationship to human connection, dependence, and well-being requires direct investigation. Findings from human friendship research cannot simply be transferred to AI systems, and ordinary chatbots should not be conflated with clinically evaluated digital interventions. The specialist article Loneliness in the Age of AI addresses this domain. The subjective experience of a user and the subjective status of an AI system are separate questions.
Frequently Asked Questions
Can you feel lonely while surrounded by people?
Yes. Loneliness depends on perceived relational adequacy and meaningful connection. A household, large network, or crowded workplace can coexist with a sense of being misunderstood or excluded. The most informative question is what type of connection feels absent.
Is loneliness a mental illness?
Loneliness is a psychological experience and measurable construct, not an independent psychiatric diagnosis. It may coexist with depression, anxiety, or other conditions, each of which requires separate clinical assessment when relevant.
Is being alone the same as being lonely?
No. Time alone can be chosen and fulfilling. Loneliness reflects an unwanted sense of inadequate social connection. Household arrangements and frequency of contact are different indicators from subjective loneliness.
Does loneliness mean that someone needs more friends?
The number of friends is only one part of a person's social circumstances. Some people need stronger reciprocity or intimacy in existing relationships; others need accessible opportunities to form new ties or a more welcoming social environment. Individual preferences matter.
Can loneliness contribute to depression or ill health?
Longitudinal research reports relationships between loneliness and later depressive symptoms and several physical-health outcomes. Some associations are reciprocal, and observational research cannot always establish causation. The appropriate response integrates relational circumstances with medical and psychological assessment. Chen et al. (2023); Wang et al. (2023).
Can loneliness improve?
Loneliness often changes with circumstances, relationship quality, opportunities, and individual coping. Some interventions reduce reported loneliness in studies, although certainty about effects and individual response remains limited. Sustainable improvement generally requires attention to the type of connection the person actually wants. Lasgaard et al. (2026).
Conclusion
Loneliness is the subjective and sometimes painful experience of inadequate social connection. Its causes range from losses and disrupted routines to unmet intimacy, limited opportunities, social exclusion, changing health, and expectations formed through experience. Its psychological consequences can affect mood, trust, attention, and everyday well-being. Scientific evidence also connects loneliness to several health outcomes, with important differences between observational associations and causal conclusions. Understanding loneliness begins with identifying the particular relationship needs and circumstances involved, and responding with opportunities for meaningful, safe, and reciprocal connection.
Related Articles
Cluster Loneliness, Friendship and Social Connection — the overarching scientific chapter on social bonds, belonging, and health.
Social Media and Loneliness: Connection, Displacement, and Individual Differences — platform-related evidence and individual variation.
Loneliness and Social Isolation in Older Adults: Differences, Risks, and Support — later-life risk factors and support.
Loneliness After a Breakup: Social Disconnection and Rebuilding Support — connection after intimate loss.
Loneliness in Marriage: Why You Can Feel Alone With Your Spouse — disconnection within an intimate partnership.
Loneliness in the Age of AI: AI Companions, Social Connection, and Emotional Dependence — the distinct evidence concerning AI companions.
Neuroticism and Loneliness: Social Perception, Isolation, and Well-Being — personality-related social perception.
Loneliness vs Social Isolation: Differences, Measures, and Examples
Social Connection: What It Means for Relationships and Health
Emotional Loneliness vs Social Loneliness: Two Patterns of Disconnection
Solitude vs Loneliness: Why Being Alone Can Feel Good or Painful
How Is Loneliness Measured? UCLA Scale and Other Research Measures
Chronic Loneliness: Social Cognition, Stress, and Self-Reinforcing Cycles
Loneliness Interventions: What Research Shows Works
How to Cope With Loneliness: Practical Steps and When to Seek Help
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