Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 3 complete abstracts (621 words), 9 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
The state of feeling sad or dejected as a result of lack of companionship or being separated from others.
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: Homesickness.
Where it fits in the MeSH classification
- Broader topics
- Emotions; Social Isolation
Research landscape
PubMed indexes 9,928 records tagged with the MeSH heading “Loneliness” (counts retrieved 2026-10-31). 6,218 of them (62.6%) were published from 2020 onward, and the busiest period so far is 2020 onward with 6,218 records.
Reviews account for 793 records (8.0%) and meta-analyses for 172. Randomized controlled trials number 284 (2.9%) as a share of all records on the topic.
Show the data
| Period | Records |
|---|---|
| through 1999 | 751 |
| 2000-2009 | 790 |
| 2010-2019 | 2,169 |
| 2020 onward | 6,218 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 793 | 8.0% |
| Meta-analyses | 172 | 1.7% |
| Randomized controlled trials | 284 | 2.9% |
Method: PubMed query "Loneliness"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.
Reading the evidence in psychiatry and psychology
Research on mental health and behaviour relies on questionnaires, interviews and rating scales rather than physical measurements, so how a condition was defined and measured shapes every result. Many studies are observational or small, placebo responses can be large, and findings in one group or culture may not carry over to another. Nothing on this page is advice about diagnosis or treatment; anyone worried about their mental health should talk to a qualified clinician. Check how outcomes were measured, who took part and how long they were followed.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
| Study / authors | Year | Source label / design | Europe PMC citations | Licence / source |
|---|---|---|---|---|
| Hormonal and Behavioral Consequences of Social Isolation and Loneliness: Neuroendocrine Mechanisms and Clinical Implications | 2025 | Review article Design not recorded in structured metadata | 6 | cc by PMID 41515962 · DOI · PMC12786008 |
| Impact of loneliness on health in healthy populations: A meta-analysis | 2026 | Meta-analysis Design not recorded in structured metadata | 5 | cc by PMID 41355074 · DOI · PMC12683082 |
| Loneliness, Anxiety Symptoms, Depressive Symptoms, and Suicidal Ideation in the All of Us Dataset | 2026 | Research article Design not recorded in structured metadata | 3 | cc by PMID 41779392 · DOI · PMC12961520 |
Hormonal and Behavioral Consequences of Social Isolation and Loneliness: Neuroendocrine Mechanisms and Clinical Implications [1]
Abstract reading summary — source excerpts
- Opening excerpt
- Social isolation and loneliness represent critical psychosocial stressors associated with profound hormonal dysregulation and adverse behavioral outcomes.
- Closing excerpt
- Understanding the endocrine-behavior interface in social disconnection offers opportunities for targeted interventions addressing this growing public health challenge.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (153 words)
Social isolation and loneliness represent critical psychosocial stressors associated with profound hormonal dysregulation and adverse behavioral outcomes. This review synthesizes current evidence on neuroendocrine mechanisms linking perceived and objective social disconnection to health consequences, emphasizing hypothalamic-pituitary-adrenal axis dysfunction, altered glucocorticoid signaling, and inflammatory pathways. Loneliness activates conserved transcriptional responses with upregulated proinflammatory gene expression and downregulated antiviral responses, mediated through sustained cortisol elevation and glucocorticoid resistance. Neural circuit alterations in reward processing, particularly the ventral tegmental area-nucleus accumbens pathway, contribute to anhedonia, social withdrawal, and cognitive decline. Sex differences in neuroendocrine responses reveal distinct hormonal profiles and circuit-specific adaptations. Emerging interventions targeting oxytocin and arginine vasopressin systems, alongside behavioral approaches addressing loneliness-induced cognitive biases, show promise. Critical research gaps include a mechanistic understanding of epigenetic modifications, sex-specific therapeutic responses, and translational applications across diverse populations. Understanding the endocrine-behavior interface in social disconnection offers opportunities for targeted interventions addressing this growing public health challenge.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41515962 · DOI · PMC12786008
Impact of loneliness on health in healthy populations: A meta-analysis [2]
Abstract reading summary — source excerpts
- Opening excerpt
- ObjectivesPrevious meta-analyses have shown that loneliness is associated with poor health (r = -.
- Closing excerpt
- There are limited studies using (1) objective measurements of health outcomes in relation to loneliness, and (2) studies exploring the association among young people, highlighting a need for more work in those areas.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (225 words)
ObjectivesPrevious meta-analyses have shown that loneliness is associated with poor health (r = -.35) and sleep challenges (r = .29). However, that work is confounded by the inclusion of unhealthy populations, with chronic conditions, such as HIV, Alzheimer's disease, diabetes, and severe mental illness. This pre-registered meta-analysis (PROSPERO CRD42019119135) examined whether loneliness is linked to poorer health in healthy populations.DesignMeta-analysis.MethodsPsycINFO, ERIC, PubMed, and Web of Science were searched for articles before January 2024 to examine the association between loneliness and health outcomes (categorized as general health, physical health [functional disability], sleep function, sensory acuity, and health service use) for healthy samples.ResultsA total of 167 articles (303,643 participants; 334 effect sizes; 158 independent samples) from 36 countries were included in the meta-analysis. Loneliness is associated with worse health for healthy populations (r = -.22), with the largest effect (r = -.23) for general health. Loneliness was not related to health service use for healthy populations. Heterogeneity was substantial, with only 7.2% of the total variance attributable to sampling error, indicating that over 92% of the variability in effect sizes reflected true differences across studies.ConclusionsHigher loneliness was associated with poorer health for healthy people. There are limited studies using (1) objective measurements of health outcomes in relation to loneliness, and (2) studies exploring the association among young people, highlighting a need for more work in those areas.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41355074 · DOI · PMC12683082
Loneliness, Anxiety Symptoms, Depressive Symptoms, and Suicidal Ideation in the All of Us Dataset [3]
Abstract reading summary — source excerpts
- Opening excerpt
- ImportanceAlthough anxiety symptoms and depressive symptoms are linked with increases in suicidal ideation, they leave much of the variance in suicidal ideation unexplained.
- Closing excerpt
- Targeting and reducing loneliness may present a transdiagnostic approach to arrest the progression from anxiety and depressive symptoms toward suicidal ideation.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (243 words)
ImportanceAlthough anxiety symptoms and depressive symptoms are linked with increases in suicidal ideation, they leave much of the variance in suicidal ideation unexplained. Loneliness may mediate the links between anxiety symptoms and suicidal ideation as well as depressive symptoms and suicidal ideation.ObjectiveTo analyze the mediating role of loneliness in the association between anxiety symptoms and suicidal ideation as well as in the association between depressive symptoms and suicidal ideation.Design, setting, and participantsThis cross-sectional study used data collected between May 31, 2017, and October 1, 2023, from 62 685 US adults who completed the self-report mental health survey portion of the National Institutes of Health's All of Us Research Program.Main outcomes and measuresSelf-report surveys estimated anxiety symptoms (using the 7-item Generalized Anxiety Disorder scale), depressive symptoms (using the first 8 items of the 9-item Patient Health Questionnaire [PHQ-9]), loneliness (using the UCLA Loneliness Scale), and suicidal ideation (using item 9 of the PHQ-9). Analyses were conducted in August of 2025.ResultsThe analytic sample of 62 685 individuals had a mean (SD) age of 61.8 (16.1) years and included 40 749 women (65.0%). Anxiety symptoms (r = 0.33; P Conclusions and relevanceIn this cross-sectional study of 62 685 participants from the All of Us Research Program, loneliness partially mediated the association between anxiety symptoms and suicidal ideation as well as depressive symptoms and suicidal ideation. Targeting and reducing loneliness may present a transdiagnostic approach to arrest the progression from anxiety and depressive symptoms toward suicidal ideation.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41779392 · DOI · PMC12961520
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article Loneliness and social isolation as risk factors for mortality: a meta-analytic review [4]
- Research article Rapid Systematic Review: The Impact of Social Isolation and Loneliness on the Mental Health of Children and Adolescents in the Context of COVID-19 [5]
- Research article A meta-analysis of interventions to reduce loneliness [6]
- Research article Associations between loneliness and perceived social support and outcomes of mental health problems: a systematic review [7]
- Research article Loneliness: clinical import and interventions [8]
- Research article Loneliness and Health in Older Adults: A Mini-Review and Synthesis [9]
Full-text reviews on EvidenceLib
Open-access review articles about this topic, reproduced in full with authors, licence and references.
Loneliness and the onset of new mental health problems in the general population
Farhana Mann, Jingyi Wang, Eiluned Pearce et al. · Social Psychiatry and Psychiatric Epidemiology 2022 · CC BY 4.0
The experience of loneliness among young people with depression: a qualitative meta-synthesis of the literature
Louis Achterbergh, Alexandra Pitman, Mary Birken et al. · BMC Psychiatry 2020 · CC BY 4.0
References
- Mavrych V, Mansour GK, Hajjar AW, Bolgova O. Hormonal and Behavioral Consequences of Social Isolation and Loneliness: Neuroendocrine Mechanisms and Clinical Implications. . 2025. PMID 41515962 · DOI · PMC12786008
- Zheng Y, Qualter P, Rollano C, Hu X, Martin A, Nukui M, et al.. Impact of loneliness on health in healthy populations: A meta-analysis. . 2026. PMID 41355074 · DOI · PMC12683082
- Musacchio Schafer K, Franklin J, Embí PJ, Walsh CG. Loneliness, Anxiety Symptoms, Depressive Symptoms, and Suicidal Ideation in the All of Us Dataset. . 2026. PMID 41779392 · DOI · PMC12961520
- Holt-Lunstad J, Smith TB, Baker M, Harris T, Stephenson D. Loneliness and social isolation as risk factors for mortality: a meta-analytic review. Perspect Psychol Sci. 2015. PMID 25910392 · DOI
- Loades ME, Chatburn E, Higson-Sweeney N, Reynolds S, Shafran R, Brigden A, et al.. Rapid Systematic Review: The Impact of Social Isolation and Loneliness on the Mental Health of Children and Adolescents in the Context of COVID-19. J Am Acad Child Adolesc Psychiatry. 2020. PMID 32504808 · DOI · PMC7267797
- Masi CM, Chen HY, Hawkley LC, Cacioppo JT. A meta-analysis of interventions to reduce loneliness. Pers Soc Psychol Rev. 2011. PMID 20716644 · DOI · PMC3865701
- Wang J, Mann F, Lloyd-Evans B, Ma R, Johnson S. Associations between loneliness and perceived social support and outcomes of mental health problems: a systematic review. BMC Psychiatry. 2018. PMID 29843662 · DOI · PMC5975705
- Cacioppo S, Grippo AJ, London S, Goossens L, Cacioppo JT. Loneliness: clinical import and interventions. Perspect Psychol Sci. 2015. PMID 25866548 · DOI · PMC4391342
- Ong AD, Uchino BN, Wethington E. Loneliness and Health in Older Adults: A Mini-Review and Synthesis. Gerontology. 2016. PMID 26539997 · DOI · PMC6162046
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-11-04; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-11-04.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.