Chronic loneliness is associated with a range of mental health difficulties. Previous theory and research indicate that psychological interventions show promise for reducing loneliness, however, there have been no systematic reviews or meta-analyses to ascertain the efficacy of these interventions across the lifespan. The aim of this study was to synthesise, meta-analyse and explore the heterogeneity in RCTs of psychological interventions for loneliness in order to establish their efficacy.

Five databases (Ovid Embase, Ovid Medline, PsycINFO, Web of Science and CINAHL) were systematically searched in order to identify relevant studies. Included studies were required to be peer-reviewed RCTs examining psychological interventions for loneliness. Two independent coders examined the abstracts of the 3973 studies and 103 full texts, finding 31 studies that met inclusion criteria, 28 of which contained sufficient statistical information to be included in the meta-analysis. The quality of included studies was assessed using the Cochrane Risk of Bias Tool.

The 31 studies (N = 3959) that were included in the systematic review were conducted with participants from a diverse range of cultures, age groups and populations. The interventions were of mixed quality and were mostly face to face, group-based and delivered weekly. The most common type of intervention was Cognitive Behavioural Therapy (CBT).

28 studies (N = 3039) were included in a meta-analysis which found that psychological interventions significantly reduced loneliness compared to control groups, yielding a small to medium effect size (g = 0.43). Subgroup analysis and meta-regressions were conducted in order to explore heterogeneity and found that type of psychological intervention was approaching significance as a moderator of the effectiveness of psychological interventions for loneliness.

In conclusion, psychological interventions for loneliness across the lifespan are effective. This finding should inform policy makers, researchers and clinicians going forward, especially in the context of increased loneliness due to the COVID-19 pandemic. There was considerable heterogeneity in the effectiveness of the interventions, suggesting that future research should also explore what works for whom and consider personalising psychological treatment.

长期孤独与一系列心理健康问题有关。先前的理论和研究表明，心理干预有望减少孤独感，但是，还没有系统评价或荟萃分析来确定这些干预在整个生命周期中的有效性。本研究的目的是综合、荟萃分析和探索孤独心理干预随机对照试验的异质性，以确定其有效性。

为了确定相关研究，系统地搜索了五个数据库（Ovid Embase、Ovid Medline、PsycINFO、Web of Science 和 CINAHL）。纳入的研究必须是经过同行评审的 RCT，以检查孤独的心理干预措施。两名独立编码员检查了 3973 项研究的摘要和 103 篇全文，发现 31 项研究符合纳入标准，其中 28 项包含足够的统计信息以纳入荟萃分析。使用 Cochrane 偏倚风险工具评估纳入研究的质量。

 纳入系统评价的 31 项研究 ( N = 3959) 是针对来自不同文化、年龄组和人群的参与者进行的。干预措施的质量参差不齐，主要是面对面的、基于小组的和每周进行的。最常见的干预类型是认知行为疗法 (CBT)。

28 项研究 ( N  = 3039) 被纳入一项荟萃分析，该分析发现与对照组相比，心理干预显着减少了孤独感，产生了中小效应 (g = 0.43)。进行了亚组分析和元回归以探索异质性，发现心理干预的类型作为孤独心理干预有效性的调节因素正在接近显着性。

总之，针对终生孤独的心理干预是有效的。这一发现应为决策者、研究人员和临床医生提供信息，尤其是在 COVID-19 大流行导致孤独感增加的情况下。干预措施的有效性存在相当大的异质性，这表明未来的研究还应该探索什么对谁有效，并考虑个性化心理治疗。