Table 2 Social isolation and connectedness outcomes

Subjective social isolation

CMD

Changing cognitions

Conoley 1985 (USA, N = 38) [39]

Reframing vs Waitlist control

Measures of loneliness did not differ between groups at 1 month (Hedges g = 0.11, 95% CI: -0.53, 0.75),

Psychoeducation

Haslam 2019 (Australia, N = 120) [40]

Groups 4 Health social identity intervention vs TAU

The intervention group reported significantly reduced loneliness compared to the control group 2 months after baseline (Odds of reduced loneliness = 3.84, 95% CI: 1.50, 9.81)

Supported socialisation

Lloyd-Evans 2020 (UK, N = 40) [41]

Community navigator programme + routine care vs Routine care

[Feasibility trial]

Loneliness in the intervention group fell from a median De Jong Gierveld Scale score of 11 at baseline to 9 at follow up, and from 10.5 to 10 for the control group participants. This change was not significant although numbers were small

SMI

Changing cognitions

Hasson-Ohayon 2014 (Israel, N = 55) [42]

Social cognition and interaction training (SCIT) + social mentoring vs social mentoring only

Participants who completed SCIT showed significant improvement between baseline and post assessment in mean scores for social engagement compared with participants in the control group, whose scores decreased. Hedges g at end of treatment (6 months): 1.44, 95% CI: 0.84, 2.05)

Psychoeducation

Silverman 2014 (USA, N = 45) [43]

Live music therapy and Education vs Education only

Perceived social support did not differ significantly between the live music therapy and education and the education only groups after the session (Hedges g = 0.47, 95% CI: -0.13, 1.07)

Supported socialisation

Gelkopf 1994 (Israel, N = 34) [44]

Watching comedy films with others vs Watching a variety of film genres

There was no significant difference in satisfaction with social support at 4-months follow-up (control 10.66 vs comedy 15.19, F = 1.90, not significant)

Terzian 2013 (Italy, N = 357) [45]

social network intervention + TAU vs TAU only

A higher overall social network improvement—including an improvement in intimate or working relationships—was reported at year 1 for the experimental treatment patients (OR = 1.8, 95% CI 1.12, 2.80). The results were still statistically significant at year 2 ( OR = 1.84, 95% CI 1.18, 2.90)

Davidson 2004 (USA, N = 260) [46]

Matched with a volunteer partner who had a personal history of psychiatric disability vs Matched with a volunteer partner who had no history of psychiatric disabilities vs Not matched with a volunteer partner

When considering all participants, there were no significant improvements in self-reported socialisation scores between groups at end of treatment (volunteer partner with no history of psychiatric problems vs control at end of treatment (9 months): Hedges g = 0.05, 95% CI: -0.34, 0.43, volunteer partner with a history of psychiatric problems vs control at end of treatment (9 months): Hedges g: -0.11, 95% CI: -0.49, 0.28)

Sheridan 2015 (Ireland, N = 107) [47]

Supported socialisation vs monetary support

There was no group (F = 0·78, p = 0.38), or group x time effect (F = 1.33, p = 0.36) for social loneliness (Social and Emotional Loneliness Scale for Adults)

Mixed approach- supported socialisation and psychoeducation

Boevink 2016 (Netherlands, N = 163) [48]

Recovery and self-help training course “TREE Recovery programme” + TAU vs TAU

After 1 year, the patients in the TREE recovery programme did not have significantly lower loneliness scores compared to treatment as usual. (Hedges g = -0.11,95% CI: -0.44, 0.23)

Castelein 2008 (Netherlands, N = 106) [49]

Guided peer support VS TAU

There was no significant difference between groups in the extent of discrepancies between desired and received in social support at 8 months (Hedges g adjusted for baseline values: = -0.09, 95% CI: -0.29, 0.47)

Mixed mental health conditions

Supported socialisation

Rivera 2007 (USA, N = 203) [50]

Peer-assisted case management vs Standard case management

There was no significant difference between peer assisted case management and standard case management in the subjective quality of social relations at either 6 months post baseline (Hedges g = -0.08, 95% CI: -0.43, 0.26) or 12 months post baseline (Hedges g = -0.09, 95% CI: -0.43, 0.25)

Social capital

CMD

Supported socialisation

Lloyd-Evans 2020 (UK, N = 40) [41]

Community navigator programme + routine care vs Routine care

[Feasibility trial]

Median perceived social capital (social network resourcefulness) changed from 7.0 to 7.5 in the intervention group, and 11.5 to 11.0 in the control group

Objective social isolation

SMI

Changing cognitions

Hasson-Ohayon 2014 (Isreal, N = 55) [42]

Social cognition and interaction training + social mentoring vs social mentoring only

There was no significant difference between the two groups on interpersonal communication at end of treatment (6 months). Hedges g = -0.06, 95% CI: -0.60, 0.48

Pos 2019 (Netherlands, N = 99) [51]

CBT for social activation vs TAU

There were no significant between group differences in social withdrawal at either 3 months post baseline (Hedges g = -0.04, 95% CI: -0.43, 0.36) or 9 months post baseline (Hedges g = 0.03, 95% CI: -0.36, 0.43)

Pot-Kolder 2018 (Netherlands, N = 116) [52]

Virtual reality CBT vs TAU

Differences between groups in the amount of time spent with others at end of treatment or 6 months post baseline were not significant

Hedges g at end of treatment (3 months) = 0.31, 95% CI: -0.06, 0.67, Hedges g at follow up (6 months) = 0.29, 95% CI: -0.08, 0.65

Roberts 2014 (USA, N = 66) [53]

Social cognition and interaction training vs TAU

The Global social functioning scale did not exhibit a Treatment group x Time interaction but did show a statistically significant main effect for treatment group, F(1, 56) = 5.65, P < .05. Follow-up analyses revealed that SCIT participants received higher global functioning ratings than TAU participants when controlling for baseline scores at 6 months (P < .05). Accordingly, the SCIT group showed a small to medium effect size advantage over TAU at follow-up (d = .43)

Social skills training

Glynn 2004 (USA, N = 63) [54]

Skills training + generalization vs skills training only

Participation in clinic-based plus in vivo amplified skills training was associated with significantly greater improvements compared to clinic based only in overall adjustment (condition-by-time interaction) (F = 4.88 (1, 40), P = .04) as assessed with the Social Adjustment Scale-II at 12 months post baseline

Marder 1996 (USA, N = 80) [55]

Social skills training vs supportive group therapy

There were significant effects favouring social skills training over supportive group therapy on total social functioning at 24 months (F = 6.05, df = 1, 94, P = 0.02) when considering all patients

Supported socialisation

Gelkopf 1994 (Isreal, N = 34) [44]

Comedy films vs variety of film genres

The comedy Intervention group had significantly more distinct network members than the control group at 4 months follow-up (control 2.87 vs comedy 5.22, F = 4.87, P < 0.05)

Priebe 2020 (UK, N = 124) [56]

Matched with a volunteer partner who had no history of psychiatric disabilities vs not matched with a volunteer partner

Patients in the intervention group had significantly more social contacts after treatment, when controlling for baseline scores (adjusted difference = 0.52, 95% CI: 0.04, 0.99, P = 0.03) and the analyses comparing the groups at the 6-month follow-up showed that patients in the intervention group still had significantly more social contacts (baseline-adjusted difference = 0.73, 95% CI: 0.05, 1.40, P = 0.04)

Mixed approach- supported socialisation and psychoeducation

Castelein 2008 (Netherlands, N = 106) [49]

Guided peer support vs waitlist

A higher proportion of participants in the intervention group had a significant increase in contact with peers outside of the sessions at end of treatment (8 months) in comparison with the waitlist control condition (OR = 2.83, 95% CI: 1.59, 5.06)

Mixed approach-changing cognitions and social skills training

Granholm 2005 (USA, N = 76) [57]

Cognitive behavioural social skills training vs TAU

The treatment group reported significantly more mean social activities on the social adjustment scale compared to treatment as usual at 6 months (Hedges g = 0.60, 95% CI: 0.14, 1.06)

Mixed mental health conditions

Supported socialisation

Rivera 2007 (USA, N = 203) [50]

Peer-assisted case management vs Standard case management

Only clients receiving peer-assisted care showed a significant increase in the number of contacts from baseline to 12 months (simple effect: F = 7.25, df = 2 and 118, P < .01, η2 = .11). However, follow-up analyses revealed that this effect was due to increased contact with peer assistants and professional staff, not with family and outside friends

When considering total network size without these staff, there was no significant difference in social network size between the two groups at either end of treatment (6 months): Hedges g = 0.187, 95% CI: -0.17, 0.54 or 12 months post baseline (Hedges g = 0.22, 95% CI: -0.14, 0.58)