This is a protocol for a Cochrane Review (intervention). The objectives are as follows: • To examine the effects of structured psychological interventions, based on cognitive behavioural therapy (CBT) techniques, compared to all comparators on loneliness in adolescents, adults, and older adults with diagnoses of common mental disorders, or at risk of loneliness. • To examine the effects of structured psychological interventions, based on CBT techniques, compared to all comparators on depression severity, anxiety severity, social connectedness, or quality of life in adolescents, adults, and older adults, with diagnoses of common mental disorders, or at risk of loneliness.

BackgroundBehavioural and cognitive interventions remain credible approaches in addressing loneliness and depression. There was a need to rapidly generate and assimilate trial-based data during COVID-19.ObjectivesWe undertook a parallel pilot RCT of behavioural activation (a brief behavioural intervention) for depression and loneliness (Behavioural Activation in Social Isolation, the BASIL-C19 trialISRCTN94091479). We also assimilate these data in a living systematic review (PROSPERO CRD42021298788) of cognitive and/or behavioural interventions.MethodsParticipants (≥65 years) with long-term conditions were computer randomised to behavioural activation (n=47) versus care as usual (n=49). Primary outcome was PHQ-9. Secondary outcomes included loneliness (De Jong Scale). Data from the BASIL-C19 trial were included in a metanalysis of depression and loneliness.FindingsThe 12 months adjusted mean difference for PHQ-9 was −0.70 (95% CI −2.61 to 1.20) and for loneliness was −0.39 (95% CI −1.43 to 0.65).The BASIL-C19 living systematic review (12 trials) found short-term reductions in depression (standardised mean difference (SMD)=−0.31, 95% CI −0.51 to −0.11) and loneliness (SMD=−0.48, 95% CI −0.70 to −0.27). There were few long-term trials, but there was evidence of some benefit (loneliness SMD=−0.20, 95% CI −0.40 to −0.01; depression SMD=−0.20, 95% CI −0.47 to 0.07).DiscussionWe delivered a pilot trial of a behavioural intervention targeting loneliness and depression; achieving long-term follow-up. Living meta-analysis provides strong evidence of short-term benefit for loneliness and depression for cognitive and/or behavioural approaches. A fully powered BASIL trial is underway.Clinical implicationsScalable behavioural and cognitive approaches should be considered as population-level strategies for depression and loneliness on the basis of a living systematic review.

BackgroundBehavioural and cognitive interventions remain a credible approach in preventing loneliness and depression. There was a need to rapidly generate and assimilate trial-based data during COVID-19.ObjectivesWe undertook a COVID-19 parallel pilot RCT of behavioural activation for depression and loneliness [the BASIL-C19 trial ISRCTN94091479]. We also assimilate these data in a COVID-19 living systematic review [PROSPERO CRD42021298788].MethodsPrimary care participants (>=65 years) with long-term conditions were computer randomised to Behavioural Activation (n=47) versus care-as-usual (n=49). The single blinded primary outcome was the PHQ-9. Secondary outcomes included loneliness (De Jong Gierveld Scale). Data from the BASIL-C19 trial were included in a random effects meta-analysis of depression and loneliness.FindingsThe 12 months adjusted mean difference for PHQ-9 was -0.70 (95% CI -2.61 to 1.20) and for loneliness was -0.39 (95% CI -1.43 to 0.65). Secondary 12-month trial outcomes suggested evidence of benefit for behavioural activation.The BASIL-C19 meta-analysis (13 trials) found short-term reductions in depression (standardised mean difference [SMD]=-0.31, 95%CI -0.51 to -0.11) and loneliness (SMD=-0.48, 95%CI -0.70 to -0.27). There were few long-term trials, but there was evidence of some benefit (loneliness SMD=-0.20, 95%CI -0.40 to -0.01; depression SMD=-0.20, 95%CI -0.47 to 0.07).DiscussionWe found a signal of effect in reducing loneliness and depression in the BASIL trial. Living meta-analysis provides strong evidence of short-term benefit for loneliness and depression.Clinical implicationsScalable behavioural and cognitive approaches should be considered as population-level strategies for depression and loneliness on the basis of the living systematic review.FundingThis study was funded by National Institute for Health and Care Research (NIHR) Programme Grants for Applied Research (PGfAR) RP-PG-0217-20006.Author summaryWhy was this study done?⍰Older people with long-term conditions have been impacted by COVID-19 pandemic restrictions and have experienced social isolation. In turn, this puts them at risk for depression and loneliness, and these are bad for health and wellbeing. Psychosocial approaches, such as behavioural activation, could be helpful.⍰Trial-based evidence is needed to demonstrate if it is possible to prevent the onset, or mitigate the impact, of loneliness and depression.⍰There are few studies of brief psychosocial interventions to mitigate depression and loneliness, and it is important to know how emerging trial-based data adds to existing evidence.What did the researchers do and find?⍰There was preliminary evidence that levels of loneliness were reduced at 3 months when behavioural activation was offered.⍰At longer term (12-month) follow-up there were signals of ongoing positive impact.⍰When BASIL-C19 data were assimilated into a living systematic review there is clear evidence of impact of brief psychological interventions on depression and loneliness in the short-term. More research into the longer-term impact is needed.What does all this mean?⍰Behavioural activation now shows evidence of benefit which will be useful for policy makers in offering support to people who are socially isolated.⍰This research knowledge will be useful once the COVID-19 pandemic has passed, since loneliness is common in older populations and effective scalable solutions will be needed to tackle this problem.⍰As new trial-based data emerges, our living systematic review and meta-analysis will be updated since this is an area of active research.