case study social isolation

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Interventions to reduce social isolation and loneliness during COVID-19 physical distancing measures: A rapid systematic review

Christopher Y K Williams

Adam t townson, milan kapur, alice f ferreira, rebecca nunn, julieta galante, veronica phillips, sarah gentry, juliet a usher-smith.

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Competing Interests: The authors have declared that no competing interests exist.

* E-mail: [email protected]

Received 2020 Aug 18; Accepted 2021 Feb 2; Collection date 2021.

This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

A significant proportion of the worldwide population is at risk of social isolation and loneliness as a result of the COVID-19 pandemic. We aimed to identify effective interventions to reduce social isolation and loneliness that are compatible with COVID-19 shielding and social distancing measures.

Methods and findings

In this rapid systematic review, we searched six electronic databases (Medline, Embase, Web of Science, PsycINFO, Cochrane Database of Systematic Reviews and SCOPUS) from inception to April 2020 for systematic reviews appraising interventions for loneliness and/or social isolation. Primary studies from those reviews were eligible if they included: 1) participants in a non-hospital setting; 2) interventions to reduce social isolation and/or loneliness that would be feasible during COVID-19 shielding measures; 3) a relevant control group; and 4) quantitative measures of social isolation, social support or loneliness. At least two authors independently screened studies, extracted data, and assessed risk of bias using the Downs and Black checklist. Study registration: PROSPERO CRD42020178654. We identified 45 RCTs and 13 non-randomised controlled trials; none were conducted during the COVID-19 pandemic. The nature, type, and potential effectiveness of interventions varied greatly. Effective interventions for loneliness include psychological therapies such as mindfulness, lessons on friendship, robotic pets, and social facilitation software. Few interventions improved social isolation. Overall, 37 of 58 studies were of “Fair” quality, as measured by the Downs & Black checklist. The main study limitations identified were the inclusion of studies of variable quality; the applicability of our findings to the entire population; and the current poor understanding of the types of loneliness and isolation experienced by different groups affected by the COVID-19 pandemic.

Conclusions

Many effective interventions involved cognitive or educational components, or facilitated communication between peers. These interventions may require minor modifications to align with COVID-19 shielding/social distancing measures. Future high-quality randomised controlled trials conducted under shielding/social distancing constraints are urgently needed.

Introduction

On 11 March 2020, the World Health Organisation declared the global spread of coronavirus disease 2019 (COVID-19) a pandemic [ 1 ]. Countries around the world established escalating containment measures to reduce virus transmission, including travel bans, closure of country borders and lockdowns. In the United Kingdom, over 1.5 million people were told they must self-isolate or “shield” themselves for a period of at least 12 weeks [ 2 ]. In addition, strict social distancing guidance both in the UK and internationally advised the public to eliminate all non-essential travel and stay at home [ 3 ]. While these measures were initially eased, social distancing measures remain in place, cases and contacts are required to self-isolate, and further national lockdowns have been re-introduced across the world [ 4 – 6 ]. To date, there has been limited literature evaluating the available interventions to protect the mental health of people asked to quarantine, socially distance, or shield during the COVID-19 pandemic. This has prompted a call for high quality research on the effects of COVID-19 on mental health and how to mitigate them [ 7 ].

One possible consequence of both the shielding of vulnerable people, and the social distancing restrictions for all, is for physical separation to lead to social isolation and loneliness [ 8 ]. Social isolation refers to the objective lack of interaction with others [ 9 ]. The concept of loneliness is similar, but refers more generally to the subjective feeling of being alone [ 10 ]. Early evidence suggests almost one quarter of adults in the UK have experienced loneliness when living under lockdown [ 11 ], while the average person’s daily number of contacts has been reduced by up to 74% [ 12 ].

There is strong evidence that both social isolation and loneliness are associated with increased all-cause mortality, cardiovascular disease, depression and anxiety [ 13 ]. With large numbers worldwide at risk of social isolation and loneliness as a result of the COVID-19 pandemic, there is an urgent need to identify effective interventions to combat this public health problem. Despite the considerable existing literature on interventions that alleviate social isolation or loneliness, many interventions may not be compatible with shielding or social distancing. To provide decision-makers with the evidence needed to tackle this public health challenge, we conducted a rapid systematic review of interventions that treat social isolation and loneliness. We aimed to evaluate the current evidence-base for interventions deemed compatible with shielding/social distancing measures, and to use this to inform public health policy about the most effective types of intervention.

Search strategy and selection criteria

We conducted a rapid systematic review to provide a timely evidence synthesis to urgently inform healthcare policy decisions in the context of the COVID-19 pandemic. We followed established guidelines for conducting rapid systematic reviews [ 14 ]. The protocol was registered with the PROSPERO international prospective register of systematic reviews (CRD42020178654; https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020178654 ) and this review was reported according to the PRISMA statement [ 15 ].

We used a two-stage process to identify relevant primary studies. First, we searched Medline, Embase, Web of Science, PsycINFO, Cochrane Database of Systematic Reviews, and SCOPUS databases from inception to April 2020 for relevant systematic reviews. One author (VP) developed and conducted the search with input from CW and JUS. The following search terms were used: (“social isolat*” OR “patient isolat*” OR “emotional isolat*” OR quarantine OR “social distanc*” OR “social support” OR lonel* OR aloneness OR solitude) AND (effect* OR efficien* OR evidence OR consequence* OR impact* OR harm* OR outcome*) AND (intervention* OR promotion* OR program* OR programme* OR campaign* OR prevention) AND (“systematic review*” OR “meta-analys*”). Results in all databases were limited to English language only. Our full search strategy can be found in S1 Appendix in S1 File . Any systematic review reporting interventions that reduce social isolation/loneliness was included. Reference lists of included reviews were screened for additional relevant reviews.

Primary intervention studies from eligible systematic reviews were then retrieved and screened in the second stage, according to the following eligibility criteria. Population: participants of any age in a non-hospital setting; Intervention: all types of intervention to reduce social isolation and/or loneliness that are feasible during COVID-19 shielding measures; Comparison: relevant control group; Outcome: quantitative changes in levels of social isolation, social support or loneliness. The preprint archive MedRxiv was also searched for grey literature relating to isolation, mental health, and COVID-19 using the following search string: (covid-19 or covid19 or coronavirus or corona virus) and (loneliness or coping or mental health) and (isolation). In addition, the titles and abstracts of articles filed in the MedRxiv COVID-19 and Psychiatry and Clinical Psychology subsections were screened for relevant primary studies. Search results were exported to EndNote reference manager and duplicates removed. Rayyan QCRI web app was used to record decisions on included studies [ 16 ].

There are many instruments available that assess different aspects of social relationships. We used the framework provided by Valtorta et al to identify and categorise appropriate instruments [ 17 ]. We chose three categories to report: 1) measures of loneliness, which include subjective questions on the function of relationships; 2) measures of social isolation or social networks, which use objective, structural measures; and 3) measures of social support, which describe both the function and structure of relationships to varying degrees depending on instrument.

Reviews and primary studies that were solely aimed at patients with specific diseases (e.g Alzheimer’s, psychosis) or at minority subgroups of the population (e.g caregivers, divorced parents, bereaved individuals, soldiers, patient relatives) were excluded due to the limited applicability of interventions targeting these groups to the wider public. Only studies with a randomised (including cluster designs) or non-randomised control group were included; pre-post studies without control were excluded.

Each intervention was independently classed by two reviewers (CW and MK) according to alignment with COVID-19 shielding advice. We used March 2020 UK government guidance to inform decisions on feasibility of interventions [ 18 ]. In this guidance, shielding is defined as the avoidance of any face-to-face contact with other people outside one’s household. This advice is aimed at people medically defined as extremely vulnerable to COVID-19, whereas the wider public are advised to stay at home if possible and to maintain social distancing of two metres. We chose to use the stricter shielding guidelines to apply feasibility judgements so that interventions would be applicable to the whole population. Interventions originally conducted in a manner not in accordance with COVID-19 shielding guidance, but which may be feasible with minor modifications to the intervention protocol (e.g delivery via videoconferencing), were classed as Potentially feasible . Studies of interventions with Unclear feasibility were labelled as such, with reasons provided. Interventions were deemed Not feasible if physical contact between participants and others is considered an integral part of the intervention.

Data extraction and synthesis

Two independent reviewers (from CW, AT, MK and RN) double screened titles and abstracts. Where a definite decision to exclude could not be made, full-texts of the systematic reviews were retrieved and screened. Differences were discussed and a consensus reached; a third reviewer was used to resolve disagreements. We (CW, AT and MK) then retrieved and double screened primary studies from each included systematic review to establish whether they met the eligibility criteria.

Two reviewers extracted data using a pre-designed data extraction sheet to allow standardised reporting of results across studies. We extracted information about: (1) study characteristics including year, location, study design, target participants, age and gender; (2) the intervention; (3) total number of participants in intervention and control groups; (4) intervention duration and follow-up; and (5) study outcomes. Where possible, change-from-baseline effect sizes were calculated using Morris’ 2008, Eq 8 method for estimating effect size from pretest-posttest-control group designs [ 19 ]. The direction of effect sizes was standardised so that a positive value indicates improvement. We were unable to perform a meta-analysis due to the heterogeneity of interventions and the incomplete effect size data. Instead, we conducted a narrative synthesis of evidence for interventions affecting the three outcomes described above: loneliness, social isolation and social support.

Intervention categories

Interventions were categorised using the framework outlined by Gardiner et al [ 20 ], which describes six groups using thematic analysis based on the purpose and mechanism of action: social facilitation interventions; psychological therapies; health and social care provision; animal interventions; befriending interventions; and leisure/skill development. The social facilitation category describes interventions with the main purpose of facilitating social interaction between peers, aiming to mutually benefit all involved participants. This contrasts befriending interventions, where the focus is on forming new friendships usually with volunteers to support the lonely individual. Psychological therapies use trained therapists to deliver recognised psychological or cognitive interventions, while health and social care provision involves support from health or social care professionals. Animal interventions use real or artificial animals as the focus of the intervention, while the leisure/skill development category is a broad classification of interventions that provide leisure activities or promote learning a new skill. We used an additional category, educational programme, for interventions that mainly seek to educate participants on topics relevant to social isolation/loneliness, or on health and well-being more generally.

Risk of bias assessment

Two reviewers (CW and AF) independently assessed risk of bias. We used the Downs and Black tool [ 21 ] due to its suitability for both randomised and non-randomised studies. Differences of opinion were resolved by consensus. Downs and Black score ranges were given the following quality levels: excellent (26–28); good (20–25); fair (15–19); and poor (≤14).

Fig 1 summarises the search and selection process. The systematic literature search retrieved 2914 unique titles/abstracts. We retrieved and screened 159 at full-text level and included 57 relevant systematic reviews. Bibliography searches of these 57 systematic reviews identified a further 10 eligible systematic reviews. From the 67 included systematic reviews, a total of 687 full-text articles were screened and 604 excluded, leaving 83 articles reporting on 81 randomised and non-randomised controlled studies for analysis.

Fig 1. PRISMA flow diagram.

From these 81, twelve studies reported interventions deemed Feasible under COVID-19 shielding guidelines. These include videoconferencing programs (n = 2), telephone befriending (n = 2), animal interventions (n = 3), a task framing intervention (n = 1) and several online/virtual programs (n = 4). In 34 studies, interventions were classed as Potentially Feasible . For these interventions, it was considered that the core part of the intervention could be conducted remotely using telephone or video call technology. For 12 interventions, feasibility was Unclear due to uncertainty over the degree of physical contact required.

A further twenty-three interventions were deemed Not feasible or only Part feasible with shielding guidelines due to the requirement for physical contact and/or interaction with participants. These include ten health and social care or befriending interventions that typically involved home visits, five leisure/skill development interventions, four animal interventions, three multi-component educational programmes, and a senior centre group programme. Details of these interventions are provided in S1 Table in S1 File , and could potentially be applicable to less stringent physical distancing measures, but are excluded from the analysis below.

Of the 58 included studies, 45 were randomised controlled trials and 13 were non-randomised controlled or quasi-experimental studies. None of the studies had been conducted during the COVID-19 pandemic. Main study characteristics including target participants, setting, age and gender distribution are reported in S2 Table in S1 File . There was considerable heterogeneity in the nature and type of interventions identified. The Leisure/skill development category had the greatest number of interventions reported (n = 20), followed by Psychological therapy (n = 14), Educational programmes (n = 8), Social facilitation (n = 7), Animal interventions (n = 3), Befriending interventions (n = 3), and Health and Social Care provision (n = 3).

Quality assessment using the Downs and Black tool revealed many studies (n = 37) were of “Fair” quality (S3 Table in S1 File ). 14 studies were judged to be “Good” quality with low risk of bias, while seven were judged to be “Poor” quality studies. Common concerns include a lack of blinding and insufficient reporting of participant loss to follow up: only 11/58 studies reported detailed information on the characteristics of participants lost to follow up, while 32/58 studies did not account for missing follow-up data in their analysis. Due to the nature of interventions, most studies did not blind participants to trial arm, leading to a high risk of performance bias, while detail on blinding of researchers was often missing.

Intervention effects on loneliness

Loneliness was the most frequently measured outcome, used in 45 studies (Tables 1 and 2 ). Most studies used established questionnaires when assessing loneliness, including the UCLA Loneliness scale and the De Jong Gierveld Loneliness scale; a minority used generic questions such as “Do you feel lonely?” [ 22 , 23 ]. Ten studies reported social isolation and/or social support outcome measures in addition to loneliness.

Table 1. Summary of results.

NRCT = non-randomised controlled trial; RCT = randomised controlled trial

Table 2. Intervention effects on loneliness.

Ordered by intervention type then author. AOKL = Ando–Osada–Kodama loneliness scale; CCSL = Chinese college student loneliness scale; DJGL = de Jong Gierveld loneliness scale; DJGL-EL = de Jong Gierveld loneliness scale, emotional loneliness subscale; DJGL-SL = de Jong Gierveld loneliness scale, social loneliness subscale; ES = effect size (standardised mean difference); HLS-3 = Hughes 3-item Loneliness scale; HSSBS = Hsuing Social Support Behaviours scale; ILS = Intimate Loneliness scale; NRCT = non-randomised controlled trial; PLS-7 = Paloutzian 7-item loneliness scale; RCT = randomised controlled trial; SLS = Social Loneliness scale; SSBS = Social Support Behaviours scale; UCLA = University California Los Angeles loneliness scale (1980); UCLA-3 = University California Los Angeles loneliness scale (3-item); UCLA-4 = University California Los Angeles loneliness scale (4-item); UCLA-I = University California Los Angeles loneliness scale, intimate subscale; UCLA-S = University California Los Angeles loneliness scale, social subscale; UCLAv3 = University California Los Angeles loneliness scale version 3 (1996). † Effect size reported in study results.

Among the most effective interventions for loneliness were those in the Psychological therapies category. Two good quality RCTs of mindfulness-based interventions demonstrated a significant improvement in loneliness [ 24 , 25 ], as did a weekly Tai Chi Qigong meditation class [ 26 ], and a laughter therapy intervention [ 27 ]. There were mixed results for reminiscence therapy, where events and experiences from the past are discussed—one RCT demonstrated significant improvement in loneliness scores compared to standard care [ 28 ], whereas Westerhof (2018) reported improvement using per-protocol but not intention-to-treat analysis [ 29 ]. Two cognitive-based interventions resulted in improved loneliness scores [ 30 , 31 ], while two others had no significant effect [ 32 , 33 ].

Most Animal interventions were deemed non-feasible, but two robot-based animal studies significantly improved UCLA Loneliness scores [ 34 , 35 ]. The latter study found that both robotic dogs and living dogs led to similar reductions in loneliness compared to no intervention, but was judged to be of poor quality. One avian companionship intervention involving a live budgerigar did not report significant results [ 36 ]. None of the three studies reporting Befriending interventions showed significant effects: Mountain’s (2014) study ended early due to inadequate recruitment [ 37 , 38 ]; Heller (1991) found no significant improvement in loneliness [ 39 ]; and Schulz (1976) reported a significant difference but at a p value of < 0.063 [ 40 ]. Additionally, neither of the two Health and Social Care provision interventions were shown to reduce loneliness [ 41 , 42 ].

The content of different Educational programme interventions varied—some focused on theories of loneliness and social integration while others sought to educate on health and well-being more generally. Lessons on friendship and social integration typically decreased loneliness, with three of four studies showing improvement in De Jong Gierveld Loneliness scores compared to control [ 43 – 45 ], though the improvement in Tilburg’s (2000) study did not reach statistical significance [ 43 ].

Conflicting evidence was found in support of Social facilitation interventions to reduce loneliness. One high quality randomised controlled study of a dedicated software program (PRISM) featuring internet access, resource guides and an email feature intended to foster connectivity showed significantly decreased loneliness scores post-intervention [ 46 ]. Two lower quality cluster-randomised studies demonstrated the effectiveness of videoconferencing programs [ 47 , 48 ], while two out of three studies of group meetings and/or networking between peers were not found to reduce loneliness [ 49 , 50 ]. The third of these studies [ 51 ] which did report a significant result was substantially higher in quality and involved a group-based educational, cognitive and social support programme designed to improve community knowledge and networking.

Interventions in the Leisure/skill development category varied greatly, and many were not effective. Among these are four out of five computer training interventions covering basic computer use, email and internet applications [ 52 – 55 ], and four exercise-related interventions [ 56 – 59 ]. One of these exercise programmes (McAuley 2000) compared aerobic exercise with stretching and toning, and reported improved loneliness in both groups at 6 but not 12 months [ 56 ]. Similarly, Dowd et al. (2014) compared two exercise groups which framed exercise either as beneficial for social skills or as beneficial for health—reduced loneliness was found in both exercise groups post-intervention, but with no difference between them [ 59 ]. In contrast, two of three gaming interventions were found to be effective at reducing loneliness [ 60 , 61 ], while the third compared gaming alone and gaming with either an adolescent or elderly person, finding no difference between groups [ 62 ]. One study of an indoor gardening programme in a nursing home, where participants were given their own plants and taught how to look after them, reported decreased loneliness scores among participants of the programme [ 63 ].

Intervention effects on social isolation

Fourteen studies reported on social isolation using a variety of instruments that measure isolation, social networks, or number of social contacts (Tables 1 and 3 ). Most interventions fell under the Leisure/skill development , Psychological and Social facilitation categories, and few reduced social isolation. Notably, a twice weekly activity session decreased social isolation [ 64 ], while group meetings between neighbours led to increased social contact despite not significantly altering loneliness levels [ 49 ]. In contrast, a mutual help network of residents in an apartment building was not found to significantly increase social ties [ 65 ].

Table 3. Intervention effects on social isolation.

Ordered by intervention type then author. ES = Effect size (standardised mean difference); HFS = Hawthorne Friendship scale (social connectedness); LSNS = Lubben Social Network Scale; NE = Network embeddedness scale; NRCT = Non-randomised controlled trial; NST = Number of social ties; PIS = Perceived isolation scale; RCT = Randomised controlled trial; SCm = Social Contacts measure; SD = Social disconnectedness scale; SIS = Social isolation scale; SNm = Social network measure. † Effect size reported in study results.

Of the two gardening-related interventions, the indoor gardening programme increased participants’ social networks within a nursing home [ 63 ], whereas a poor quality study evaluating horticultural therapy was not found to improve social connectedness [ 66 ]. Logotherapy, a meaning-oriented therapy that helps individuals appreciate their existence, was associated with decreased social disconnectedness and isolation [ 67 ], while Tai Chi Qigong classes and Saito’s (2012) social support programme did not increase social networks despite improving feelings of loneliness [ 26 , 51 ]. As previously seen with loneliness outcomes, telephone befriending [ 39 ], computer training [ 55 ], and exercise programmes had no significant effect on measures of social isolation [ 68 – 70 ].

Intervention effects on social support

Eighteen studies reported on social support using the Duke Social Support, Perceived Social Support, Multidimensional Perceived Social Support, and Medical Outcomes Study Social Support scales, among others (Tables 1 and 4 ). Just as for loneliness, Psychological interventions were the most successful at increasing social support. In particular, mindfulness therapy [ 71 ], visual art discussions [ 72 ], Tai Chi Qigong meditation [ 26 ], and a cognitive enhancement programme were found to improve social support [ 31 ]. In contrast, Befriending , Educational , and Health and Social Care provision interventions did not have any significant effects. Mixed evidence was found for Social facilitation interventions that improved social support. Three studies reported significant results—these include the PRISM software program and the social support programme described previously [ 46 , 51 ], while one of the two videoconferencing programs reported significantly improved social support scores at 1 week but not 3 months [ 48 ].

Table 4. Intervention effects on social support.

Ordered by intervention type then author. DSSI = Duke Social Support Index; ES = Effect size (standardised mean difference); HSSBS = Hsuing Social Support Behaviours scale; ISEL = Interpersonal Support Evaluation List; ISSI = Interaction Schedule for Social Interaction; MOS-SSS = Medical Outcomes Study Social Support Survey; MSPSS = Multidimensional Scale of Perceived Social Support; NRCT = Non-randomised controlled trial; PSSS = Perceived Social Support scale; RCT = Randomised controlled trial; RSSQ-NP = Revised Social Support Questionnaire, total number of people; RSSQ-S = Revised Social Support Questionnaire, total satisfaction; Social connection (UCLA/MOS-SSS) = Social Connection factor incorporating UCLA loneliness scale and MOS-SSS; SICA = Social Interaction Complete Amount; SPS = Social Provisions Scale; SS-A = Social Support Appraisal scale; SS-B = Social Support Behaviours scale; SSBS = Social Support Behaviours scale; SSm = Social support measure; SSS = Social Support satisfaction. † Effect size reported in study results

Effective interventions for specific population groups

Of the 58 included studies, a majority (n = 51) targeted older adults. These studies were typically conducted either in the community, at day-care centres, in nursing homes, or within other types of residential care facility. In total, 17 studies were conducted in nursing or care facilities. Effective interventions in this setting include weekly visits from an interactive robotic dog or seal [ 34 , 35 ], Wii gaming [ 60 ], gardening [ 63 ], videoconferencing [ 47 , 48 ], and cognitive/psychological interventions [ 27 , 28 , 31 ]. A further six interventions were conducted in retirement homes or communities, among which only Wii gaming was found to be effective [ 61 ].

There was a female majority among study participants in all but five studies, and seven were exclusively open to female participants [ 32 , 39 , 43 , 49 , 72 – 74 ]. Of these, visual art discussions and neighbourhood group meetings were effective at reducing loneliness and social isolation respectively [ 49 , 72 ], while educational well-being meetings were associated with a non-significant improvement in loneliness [ 74 ]. In contrast, conflicting evidence for a friendship enrichment programme was found [ 43 , 73 , 75 ], and a telephone befriending study of female residents in low-income housing was not effective [ 39 ].

Finally, six studies targeted student populations studying at university or college and all involved a psychological or cognitive component. Among the effective interventions were two Mindfulness-based therapies, one trialled in a university community and the other recruiting lonely college students, in addition to a cognitive behavioural intervention at a university counselling centre [ 25 , 30 , 71 ]. Cognitive reframing sessions for female undergraduate psychology volunteers and the “Lonely? Unburdening your Vulnerability” (LUV) programme for college students were ineffective, as were attempts to frame exercise as beneficial for social skills among inactive university students [ 32 , 59 , 76 ].

To our knowledge, this is the first systematic review of interventions for social isolation and loneliness that can be applied during the COVID-19 pandemic or other situations where social distancing is required. We identified 58 studies of interventions to reduce social isolation, social support and loneliness that may be feasible with shielding/social distancing guidelines. There was significant heterogeneity in the interventions identified, and we found mixed results across the intervention categories.

Many Psychological therapy interventions were effective, with studies of mindfulness-based therapies, Tai Chi Qigong meditation, laughter therapy and visual art discussions demonstrating significant improvements in loneliness or social support outcomes. These represent potentially low-cost interventions that can be conducted in online groups on a large scale. Additionally, while Educational programme interventions varied greatly in both procedure and overall results, several studies found that lessons on making friends and addressing barriers to social integration had a positive effect on loneliness. These findings collectively suggest a possible underlying cognitive aspect to loneliness, which may be targeted either directly using psychology-based interventions, or indirectly by exploring the causes of one’s loneliness and practising the development and maintenance of social relationships [ 77 ].

When considering interventions aiming to increase contact with others, more evidence was found in support of Social facilitation interventions compared with Befriending interventions to reduce loneliness. The former category involves facilitating interaction between peers, whereas the latter focuses on actively making new friendships. The stronger evidence for Social facilitation found in this review suggests that providing a means for isolated or lonely people to interact with their existing social circles may be more beneficial than making new friends. However, these findings should be interpreted with caution as few studies on befriending interventions were identified. Future high-quality randomised studies of befriending, and in particular telephone befriending, are required to further evaluate its effectiveness.

It is generally accepted that the COVID-19 pandemic has had a disproportionate effect on vulnerable groups, widening pre-existing socioeconomic, race, gender and other inequalities across the population [ 7 , 78 , 79 ]. Most of the studies reported in this review were found to target older adults, either in the community or in residential, nursing and care homes. Loneliness and social isolation within nursing and care homes has received particular attention due to policies prohibiting family visits and social gatherings at these facilities due to COVID-19 [ 80 , 81 ]. We found evidence in support of cognitive/psychological interventions, videoconferencing, Wii gaming, gardening and robotic pets as effective interventions in these settings.

Growing evidence suggests that women, ethnic minorities, young adults, and people with lower education or income are at a significantly increased risk of being lonely as a result of the pandemic [ 82 , 83 ]. We found few studies aimed at young adult or student populations, who may be more vulnerable to loneliness if isolating away from home for prolonged periods. All included studies in this age group involved a psychological or cognitive component, with Mindfulness-based and cognitive-behavioural therapies proving effective. Whether the other categories of interventions identified in this review are similarly effective among young adults is not known. Likewise, very few interventions were identified that specifically target individuals of lower socioeconomic status or ethnic minorities.

Many of the effective interventions in this review will require telephone or video call technology to carry out the intervention during COVID-19 shielding measures. This has implications for the accessibility of each intervention: the costs of the technology required to deliver interventions may restrict participants by socioeconomic status, while the minimum level of digital literacy required may prevent its use among people with lower education [ 84 , 85 ]. There is a considerable risk that those who are most likely to be lonely or isolated—and hence most in need of interventions—will not possess, or know how to use, electronic devices and/or a high-speed internet connection to facilitate intervention delivery. Any approach to help people suffering from loneliness or social isolation must therefore take these issues into consideration.

Since starting this review, the UK Government has announced a £5 million Loneliness COVID-19 Grant Fund for national organisations working to tackle loneliness [ 86 ]. This aims to support charities currently offering services such as telephone befriending and community volunteering schemes [ 87 , 88 ]. In addition, the NHS.uk website provides both support for people feeling lonely and onward referral for psychological therapies if appropriate [ 89 ]. This review expands on the current provision of available services for lonely or isolated individuals and presents the evidence for alternative interventions that comply with COVID-19 distancing measures. We believe a combination of educational and psychological approaches that target the root cause of one’s loneliness, in addition to social facilitation initiatives to create and maintain relationships, represent the best opportunities to improve loneliness. It is imperative that researchers and policymakers work together to develop safe, effective programmes that alleviate loneliness and social isolation, while simultaneously addressing the digital, socioeconomic and generational inequalities that may result from unequal access to interventions.

One strength of our analysis is the use of official March 2020 UK government guidance on shielding. This provided an objective method by which to assess the feasibility of interventions. Similar guidance is in place worldwide, so our findings are likely generalizable to other countries. Due to the changing severity of government distancing regulations, we focused on interventions deemed feasible, some with modification, under the most stringent restrictions. Feasible interventions can therefore be conducted irrespective of future, more lenient changes to government policy. Many interventions could also be delivered without modification as restrictions are eased. Moreover, we followed established guidance on the conduct of rapid reviews, performing a systematic review of systematic reviews to generate the final list of primary studies to be screened. This method allowed a broad and comprehensive review of the existing literature and enabled large numbers of potentially relevant studies to be identified. However, as we were dependent on the search strategy and selection criteria of the reviews identified by our initial search, some relevant studies not reported in a review may have been omitted. We sought to mitigate this by searching the pre-print archive MedRxiv for the most recently published studies.

Limitations

Our review has several limitations. First, many studies were found to be of “Fair” quality when assessing risk of bias. This was generally because studies did not adequately account for participant loss to follow up, while the nature of many mental health-related interventions means blinding is often not possible. Second, the extent to which our findings can be applied to the entire population is unclear. The country and setting in which interventions were carried out varied, while older adults were the target participants of most studies. Whether the interventions included in this study are similarly effective in younger age groups is not known. It is of paramount importance that effective interventions targeting each age group across different settings are available. Third, there is much to discover about the types of loneliness across different groups affected by the pandemic and ensuing lockdown. Greater understanding of the differences between these groups, and the underlying processes driving various states of wellbeing, would provide a better foundation to develop interventions that treat loneliness and social isolation for all.

In conclusion, this review presents the current evidence for interventions targeting social isolation or loneliness that may be compatible with shielding/social distancing measures. Most effective interventions for loneliness either involved cognitive or educational components, or facilitated communication and networking between peers; we found few effective interventions for social isolation. Delivery of available interventions may require modification to align with COVID-19 shielding/social distancing measures—many interventions involved physical contact in their original protocol but were deemed feasible using telephone or video call technology. This has implications for the accessibility of interventions to the wider public. Future high-quality randomised controlled trials conducted under the constraints of shielding/social distancing are urgently needed to build on the findings of this review.

Supporting information

Data availability.

All relevant data are within the paper and its Supporting Information files.

Funding Statement

The author(s) received no specific funding for this work. JG was funded by the National Institute for Health Research Applied Research Collaboration East of England (grant RNAG/564) for time spent on this project. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care.

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Additional Editor Comments:

This is an interesting timely and well conducted review.

The abstract is well written and comprehensive.

Introduction: it might be useful to update this to the current situation with regard to COVID-19 in the UK and internationally particularly around restrictions being rei-mposed.

Methods: Well described and seems robust. The categories of loneliness reported are justified. Exclusions are justified. One limitation is that more recent studies - those not included in a review - will not be captured by the methodology. This decision (to do a rapid review) should be more clearly justified In the method. Narrative synthesis is justified.

Results: Would it also be worth thinking about interventions that would be feasible under strict covert measures, but not quite shielding, which seems to be the current situation in the UK at the moment? I think this would just require another section/ paragraph in the results. It would be good to know which categories of Gardiner's framework the non-viable and unclear interventions were in. It would have been good to look at the effectiveness of the programmes on different populations; for example, older people who may be particularly vulnerable and at risk during COVID-19 restrictions - there is an oblique reference to this in the discussion (second paragraph on page 16) but it should be made more explicit that older adults are a vulnerable category.

Discussion: Rather than interventions that target the whole age population, would it not be better to think about future interventions that are targeted at specific age groups?

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

2. Has the statistical analysis been performed appropriately and rigorously?

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

4. Is the manuscript presented in an intelligible fashion and written in standard English?

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Many thanks to the authors for this submission. This research offers a timely and original contribution to the rapidly emerging Covid-19 field of research.

The rationale and methodological approaches are transparent and have been expertly managed to produce the review.

The findings and implications of the rapid review are of relevance across a number of professional disciplines as well as for policy and practice in helping to inform responses which offer evidence based interventions to reduce social isolation at this time.

Two additional aspects to the review could be considered. One is touched upon on line 357. 1) Addressing inequality in access/inclusion, inclusive of digital literacy could be more fully considered. A couple of ways this would be addressed is by highlighting if any of the reviewed studies provide a blueprint/demonstrate good practice in the area of accessibility for groups at risk of inequality in access such as older age adults - many of whom are facing the highest levels of social isolation (previously shielding). Some references to those populations who are facing highest levels of social isolation and loneliness would be valuable to evidence, so thought can be given to the design/tailoring to the populations affected. At the moment, the review is perhaps quite homogeneous in how it considers social distancing/covid related measures on 'people'. However as said previously, we know that this pandemic is reinforcing inequalities within specific populations such as those on low income, older age adults, BME groups (cultural competency and representations of mental health may be relevant to mention). It is possible to pull out a bit more about the participant/population characteristics from the review? Furthermore, 2) it may be valuable to align some of the findings to existing social support which has been offered through Government_ NHS provision during Covid-19 period thus far. A quick check indicates that these are broadly psychoeducational, befriending in local community and psychological referral. It would be valuable to make a link in discussion which situates the findings of the review within a comment to current provision and how this provision can be improved, re-orientated to take into account the review findings about efficacy of interventions. Many thanks again for submitting this research article.

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Reviewer #1:  Yes:  Dr Kate Reid

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Author response to Decision Letter 0

Collection date 2021.

18 Nov 2020

Response to reviewers

Authors: We would like to thank the academic editor and reviewer for their helpful comments. Our detailed point-by-point responses are provided below.

Editor: This is an interesting timely and well conducted review.

Authors: Many thanks for your kind comments.

Editor: The abstract is well written and comprehensive.

Editor: Introduction: it might be useful to update this to the current situation with regard to COVID-19 in the UK and internationally particularly around restrictions being reimposed.

Authors: We agree. We have updated lines 75-77 (of the tracked-changes manuscript) to reflect the re-introduction of national lockdowns.

Editor: Methods: Well described and seems robust. The categories of loneliness reported are justified. Exclusions are justified. One limitation is that more recent studies - those not included in a review - will not be captured by the methodology. This decision (to do a rapid review) should be more clearly justified In the method. Narrative synthesis is justified.

Authors: We agree. We have clarified the need to conduct a rapid review to urgently inform healthcare policy decisions in lines 105-106. Furthermore, we have acknowledged as a limitation in the Discussion that some recent studies may not have been captured and explained how we sought to mitigate this.

Editor: Results: Would it also be worth thinking about interventions that would be feasible under strict covert measures, but not quite shielding, which seems to be the current situation in the UK at the moment? I think this would just require another section/ paragraph in the results.

Authors: Within the 58 studies, we have already included all the interventions which do not entirely meet the shielding measures, but would be feasible with modification (these were classed as “Potentially Feasible”, and required modification to bring them in alignment with the principles of shielding). We feel that with the ongoing changes to government COVID-19 restrictions, a standardised approach to classify interventions using the original definition of shielding is most appropriate. Included interventions will therefore be feasible regardless of the current severity of restrictions and will remain feasible as these restrictions change in the future.

Editor: It would be good to know which categories of Gardiner's framework the non-viable and unclear interventions were in.

Authors: We have expanded the paragraph on “Not feasible” or only “Part feasible” interventions to also detail the types of interventions that were excluded. Full details of these interventions can be found in Supplementary Table 1.

Editor: It would have been good to look at the effectiveness of the programmes on different populations; for example, older people who may be particularly vulnerable and at risk during COVID-19 restrictions - there is an oblique reference to this in the discussion (second paragraph on page 16) but it should be made more explicit that older adults are a vulnerable category.

Authors: We are grateful for this suggestion. We have added a subsection to the Results that covers effective interventions for vulnerable groups. Furthermore, in the Discussion we have discussed the current provision for interventions targeting certain vulnerable groups.

Editor: Discussion: Rather than interventions that target the whole age population, would it not be better to think about future interventions that are targeted at specific age groups?

Authors: We agree. We have re-structured the Discussion to consider different age groups.

Reviewer 1:

Reviewer: Many thanks to the authors for this submission. This research offers a timely and original contribution to the rapidly emerging Covid-19 field of research.

Reviewer: The rationale and methodological approaches are transparent and have been expertly managed to produce the review.

Reviewer: The findings and implications of the rapid review are of relevance across a number of professional disciplines as well as for policy and practice in helping to inform responses which offer evidence based interventions to reduce social isolation at this time.

Reviewer: Two additional aspects to the review could be considered. One is touched upon on line 357. 1) Addressing inequality in access/inclusion, inclusive of digital literacy could be more fully considered. A couple of ways this would be addressed is by highlighting if any of the reviewed studies provide a blueprint/demonstrate good practice in the area of accessibility for groups at risk of inequality in access such as older age adults - many of whom are facing the highest levels of social isolation (previously shielding). Some references to those populations who are facing highest levels of social isolation and loneliness would be valuable to evidence, so thought can be given to the design/tailoring to the populations affected. At the moment, the review is perhaps quite homogeneous in how it considers social distancing/covid related measures on 'people'. However as said previously, we know that this pandemic is reinforcing inequalities within specific populations such as those on low income, older age adults, BME groups (cultural competency and representations of mental health may be relevant to mention). It is possible to pull out a bit more about the participant/population characteristics from the review?

Authors: We agree. We have added sections to the Results and Discussion which discusses the availability of interventions for vulnerable groups and highlighted the lack of effective interventions for some of these groups. We were unable to find studies providing a blueprint for increasing the accessibility of interventions, however we have warned of the necessity to consider accessibility when seeking to deliver interventions in the Discussion. Likewise, we have discussed the different types of accessibility (educational, economic and infrastructure) that may be required to facilitate intervention delivery.

Authors: Full details of the participant characteristics for each study have been extracted and can be found in the Supplementary Tables. We have clarified the reference to this in line 231.

Reviewer: Furthermore, 2) it may be valuable to align some of the findings to existing social support which has been offered through Government_ NHS provision during Covid-19 period thus far. A quick check indicates that these are broadly psychoeducational, befriending in local community and psychological referral. It would be valuable to make a link in discussion which situates the findings of the review within a comment to current provision and how this provision can be improved, re-orientated to take into account the review findings about efficacy of interventions.

Authors: We agree. We have added a section to the Discussion detailing the current efforts and services for loneliness and social isolation and summarising how this review adds to this current provision. We have further highlighted the need for collaboration to improve loneliness and isolation and address the growing inequalities that may be worsened by unequal access to the currently available interventions.

Reviewer: Many thanks again for submitting this research article.

Submitted filename: Response to reviewers.docx

Decision Letter 1

PONE-D-20-25726R1

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Additional Editor Comments (optional):

Your revisions have improved what was already a really interesting paper.

I have a few very minor suggestions that I spotted as I read through the revised manuscript. I hope these are helpful as you make the final preparations for publication.

Ln 150-154 – you might want to think about the tense here

Ln 204 should be Figure 1, not Fig 1

Ln 284 I don’t think commas are needed here : these studies, which did report a significant result, was

Ln 436-440 -consider which tenses are best to use here

Ln 445-447 The following sentence is a bit clumsy and this hard to follow “We sought to mitigate this by searching the pre-print archive MedRxiv for the most recent studies, while included reviews were published as recently as 2020.”

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

2. Is the manuscript technically sound, and do the data support the conclusions?

3. Has the statistical analysis been performed appropriately and rigorously?

4. Have the authors made all data underlying the findings in their manuscript fully available?

5. Is the manuscript presented in an intelligible fashion and written in standard English?

6. Review Comments to the Author

Reviewer #1: Following peer review, the authors have addressed the comments and suggestions. This paper is now ready for publication. It offers a useful contribution to the field and will no doubt be beneficial to researchers and stakeholders in this area of study.

7. PLOS authors have the option to publish the peer review history of their article ( what does this mean? ). If published, this will include your full peer review and any attached files.

Acceptance letter

Dear Dr. Williams:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

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