A systematic review and meta-analysis was conducted to investigate the prevalence and antecedents/outcomes of loneliness and social isolation among individuals with severe mental disorders (SMD), such as schizophrenia, schizoaffective disorder, bipolar disorder or major depressive disorder.

Five well-known electronic databases (PubMed, PsycINFO, CINAHL, Web of Science and Scopus) were searched (plus a hand search). Observational studies that report the prevalence and, if available, antecedents and consequences of loneliness/isolation among individuals with SMD were included. Key characteristics were extracted, and a meta-analysis was performed. Our systematic review was preregistered on PROSPERO (ID: CRD42024559043). The PRISMA guidelines were followed. The Joanna Briggs Institute (JBI) standardized critical appraisal tool developed for prevalence studies was applied to assess the quality of the included studies.

The initial search yielded 4506 records, and after duplicate removal and screening, a total of 10 studies were finally included. The studies included used data from Europe, Asia, North America, and Oceania. Two studies employed a longitudinal design, while all other studies had a cross-sectional design. Most of the studies included between 100 and 500 individuals with SMD. All studies involved both male and female participants, with women typically comprising about 40% of the sample. The average age of participants often ranged from approximately 30 to 40 years. The estimated prevalence of loneliness was 59.1% (95% CI: 39.6% to 78.6%, I2 = 99.3, P < .001) among individuals with any diagnosis of SMD. Furthermore, the estimated prevalence of objective social isolation was 63.0% (95% CI: 58.6% to 67.4%) among individuals with schizophrenia or schizophrenia spectrum disorder. The quality of the studies was moderate to good. Subjective well-being and depressive symptoms in particular were found to contribute to loneliness in the included studies.

The present systematic review with meta-analysis identified high levels of loneliness and objective social isolation among those with SMD. These findings stress the importance of monitoring and addressing social needs in this vulnerable group, which may have a positive effect on the life quality of individuals with SMD. Future research in neglected regions (e.g. South America and Africa) is recommended. Different diagnoses within severe mental disorders should be distinguished in future studies. Furthermore, additional longitudinal studies are required to explore the antecedents and consequences of loneliness and social isolation among individuals with SMD.

A systematic review/meta-analysis synthesising the existing evidence regarding the prevalence of loneliness and social isolation among individuals with mild cognitive impairment (MCI) or dementia is lacking.

A systematic review and meta-analysis was conducted to investigate the prevalence and factors associated with loneliness and social isolation among individuals with MCI or dementia.

A search was conducted in five established electronic databases. Observational studies reporting prevalence and, where available, factors associated with loneliness/isolation among individuals with MCI and individuals with dementia, were included. Important characteristics of the studies were extracted.

Out of 7427 records, ten studies were included. The estimated prevalence of loneliness was 38.6% (95% CI 3.7–73.5%, I2 = 99.6, P < 0.001) among individuals with MCI. Moreover, the estimated prevalence of loneliness was 42.7% (95% CI 33.8–51.5%, I² = 90.4, P < 0.001) among individuals with dementia. The estimated prevalence of social isolation was 64.3% (95% CI 39.1–89.6%, I² = 99.6, P < 0.001) among individuals with cognitive impairment. Study quality was reasonably high. It has been found that living alone and more depressive symptoms are associated with a higher risk of loneliness among individuals with dementia.

Social isolation, and in particular loneliness, are significant challenges for individuals with MCI and dementia. This knowledge can contribute to supporting successful ageing among such individuals. Future research in regions beyond Asia and Europe are clearly required. In addition, challenges such as chronic loneliness and chronic social isolation should be examined among individuals with MCI or dementia.

Loneliness is a risk factor for late-life dementia. There is less consistent evidence of its association with cognitive performance. This study examined the replicability of the association between loneliness and overall and domain-specific cognitive function and informant-rated cognitive decline in cohorts from seven countries: the United States, England, India, China, South Africa, Mexico, and Chile.

Data were from the Harmonized Cognitive Assessment Protocol administered in seven population-based studies (total N > 20,000). Participants reported their loneliness, completed a battery of cognitive tests, and nominated a knowledgeable informant to rate their cognitive decline. Random-effect meta-analyses were used to summarize the associations from each cohort.

Loneliness was associated with poor overall cognitive performance and informant-rated cognitive decline controlling for sociodemographic factors (meta-analytic correlation for overall cognition = −.10 [95% CI = −.13, −.06] and informant-rated decline = .16 [95% CI = .14, .17]). Despite some heterogeneity, the associations were significant across samples from Africa, Asia, Europe, North, Central, and South America. The meta-analysis also indicated an association with specific cognitive domains: episodic memory, speed-attention, visuospatial abilities, numeric reasoning, and verbal fluency. The associations were attenuated but persisted when depressive symptoms were added as a covariate. Depression, cognitive impairment, and sociodemographic factors did not consistently moderate the associations across samples.

Loneliness is associated with poor performance across multiple domains of cognition and observer-rated cognitive decline, associations that replicated across diverse world regions and cultures.

Loneliness has emerged as a pervasive public health challenge. Understanding loneliness and its associated risk factors is crucial for developing interventions to address this issue effectively. This study aimed to investigate loneliness among adults living in Australia, comparing different age cohorts.

This study used 10,815, 11,234, 14,670 and 15,049 records with loneliness measurements taken at 2006, 2010, 2014 and 2018, respectively, from the Household, Income and Labour Dynamics in Australia (HILDA) survey. A supervised machine learning algorithm, CatBoost, was employed to predict loneliness. Model predictions were explained using SHapley Additive exPlanations (SHAP) and partial dependence plots across five age-based subgroups to capture life stage variations.

Mental well-being, having a life partner, social connectedness and social fulfilment were the most important predictors of loneliness at the whole-population level. Among young adults, the level of friendship fulfilment, financial satisfaction and health status were relatively strong predictors of loneliness, while loneliness in older adults was more strongly associated with spare time fulfilment, community satisfaction and the loss of loved ones. Youth who reported that they did not have a lot of friends were predicted to have a 46.5% (95% CI: 45.9%–47.2%) chance of experiencing loneliness. Seniors have a 44.9% (95% CI: 43.9%–45.8%) chance of experiencing loneliness if they were almost always not fulfilled in their spare time.

This study underscores the need to recognise the heterogeneity of loneliness across the lifecourse and the importance of both targeted strategies and efforts to improve broader social cohesion.

Loneliness has become a major public health issue of the recent decades due to its severe impact on health and mortality. Little is known about the relation between loneliness and social anxiety. This study aimed (1) to explore levels of loneliness and social anxiety in the general population, and (2) to assess whether and how loneliness affects symptoms of social anxiety and vice versa over a period of five years.

The study combined data from the baseline assessment and the five-year follow-up of the population-based Gutenberg Health Study. Data of N = 15 010 participants at baseline (Mage = 55.01, s.d.age = 11.10) were analyzed. Multiple regression analyses with loneliness and symptoms of social anxiety at follow-up including sociodemographic, physical illnesses, and mental health indicators at baseline were used to test relevant covariates. Effects of loneliness on symptoms of social anxiety over five years and vice versa were analyzed by autoregressive cross-lagged structural equation models.

At baseline, 1076 participants (7.41%) showed symptoms of social anxiety and 1537 (10.48%) participants reported feelings of loneliness. Controlling for relevant covariates, symptoms of social anxiety had a small significant effect on loneliness five years later (standardized estimate of 0.164, p < 0.001). Vice versa, there was no significant effect of loneliness on symptoms of social anxiety taking relevant covariates into account.

Findings provided evidence that symptoms of social anxiety are predictive for loneliness. Thus, prevention and intervention efforts for loneliness need to address symptoms of social anxiety.

The COVID-19 pandemic posed an unprecedented global challenge, with past evidence suggesting negative psychological effects with the additional concern that social and physical restrictions might disproportionately affect adolescents.

To explore mental health and its wider determinants in young people in the UK during 1 year of the COVID-19 pandemic (August 2020–August 2021).

A representative sample of 11 898 participants (48.7% female) aged between 13 and 19 years (mean = 16.1) participated in five waves of data collection. Using validated self-reported questionnaires for loneliness, anxiety and depression, this survey measured the extent and nature of the mental health impacts of the coronavirus pandemic and help-seeking behaviours, and changes over time.

Young people experienced higher levels of anxiety during the summer and fall 2020, followed by higher levels of depression during the winter 2020–2021, with loneliness gradually increasing then peaking during the spring and summer of 2021. Young people who were older, female, with pre-existing mental-health issues and experiencing financial difficulties were at higher risk of anxiety, depression and loneliness. Help-seeking behaviours reduced the risk of depression and loneliness.

The COVID-19 pandemic had substantial impact on young people, whether on their mental health, their social contacts and interactions or their perspective on what the future holds for them. Young people strongly advocated for better teacher training, and a better integration of mental health services, particularly within their schools.

To explore the association of cardiovascular-kidney-metabolic (CKM) health with the risk of depression and anxiety and to investigate the joint association of CKM health and social connection with depression and anxiety.

This prospective cohort study included 344 956 participants from the UK Biobank. CKM syndrome was identified as a medical condition with the presence of metabolic risk factors, cardiovascular disease, and chronic kidney disease, and was classified into five stages (stage 0–4) in this study. Loneliness and social isolation status were determined by self-reported questionnaires. Cox proportional hazards models were applied for analyses.

Compared with participants in stage 0, the HRs for depression were 1.17 (95% CI 1.10–1.25), 1.40 (95% CI 1.33–1.48), and 2.14 (95% CI 1.98–2.31) for participants in stage 1, 2–3, and 4, respectively. Similarly, participants in stage 2–3 (HR = 1.20, 95% CI 1.14–1.26) and stage 4 (HR = 1.63, 95% CI 1.51–1.75) had greater risks of incident anxiety. We found additive interactions between loneliness and CKM health on the risk of depression and anxiety. Participants simultaneously reported being lonely and in stage 4 had the greatest risk of depression (HR = 4.44, 95% CI 3.89–5.07) and anxiety (HR = 2.58, 95% CI 2.21–3.01) compared with those without loneliness and in stage 0. We also observed an additive interaction between social isolation and CKM health on the risk of depression.

Our findings suggest the importance of comprehensive interventions to improve CKM health and social connection to reduce the disease burden of depression and anxiety.

Despite the growing interest in the prevalence and consequences of loneliness, the way it is measured still raises a number of questions. In particular, few studies have directly compared the psychometric properties of very short measures of loneliness to standard measures.

We conducted a large epidemiological study of midwife students (n = 1742) and performed a head-to-head comparison of the psychometric properties of the standard (20 items) and short version (3 items) of the UCLA Loneliness Scales (UCLA-LS). All participants completed the UCLA-LS-20, UCLA-LS-3, as well as other measures of mental health, including anxiety and depression.

First, as predicted, we found that the two loneliness scales were strongly associated with each other. Second, when using the dimensional scores of the scales, we showed that the internal reliability, convergent-, discriminant-, and known-groups validities were high and of similar magnitude between the UCLA-LS-20 and the UCLA-LS-3. Third, when the scales were dichotomized, the results were more mixed. The sensitivity and/or specificity of the UCLA-LS-3 against the UCLA-LS-20 were systematically below acceptable thresholds, regardless of the dichotomizing process used. In addition, the prevalence of loneliness was strikingly variable as a function of the cut-offs used.

Overall, we showed that the UCLA-LS-3 provided an adequate dimensional measure of loneliness that is very similar to the UCLA-LS-20. On the other hand, we were able to highlight more marked differences between the scales when their scores were dichotomized, which has important consequences for studies estimating, for example, the prevalence of loneliness.