背景：老龄化速度的不断攀升随之带来了老年人这一群体出现的心理健康问题也越来越为严峻，随着晚年生活中身体机能的下降、健康状况较差、社交网络的缩小，特别是如果在生活中遇到各种负面事件，很容易产生孤独和抑郁的情绪，但老年人通常认为这样是自然衰老带来的问题而忽视其危害性，即便是遇到心理方面的困扰也不会主动去排解，导致情况愈发严重，甚至带来自杀的风险。

目的：本文研究的主要目的是了解老年人社会参与、孤独感和抑郁情绪的整体情况，研究老年人社会参与、孤独感和抑郁情绪的关系，以及孤独感在社会参与和抑郁情绪之间是否起到中介作用。

方法：本文的数据来源为2015年中国健康与养老追踪调查（CHARLS）数据，选择60岁及以上的老年人共8025个有效样本作为分析对象，描述了样本的整体特征，并用Pearson和Spearman相关分析法探讨社会参与、孤独感和抑郁情绪的关系，以线性回归和sobel的方式作中介效应检验。

结果：老年人抑郁情绪的得分均值为7.85，有28.31%的老人感到孤独，49.62%的老人在日常生活中进行社会参与。社会参与分别和抑郁情绪（r=-0.096，p<0.001）、孤独感（r=-0.047，p<0.001）呈负相关，孤独感和抑郁情绪呈正相关（r=0.487，p<0.001），孤独感在社会参与和抑郁情绪中起到中介作用。

结论：孤独感具有较为显著的中介作用，老年人通过参加社会活动，提高社会参与能力，丰富社会支持网络，有助于缓解孤独感和抑郁，以保持良好的精神状态。

Background: The aging speed rising then the mental health problems of this group is becoming more and more serious,with the decline of physical function,poor health status,social network reduction, in the face of a series of negative life events in later life,older adults are prone to have the lonely and depressed mood,but old adults often think this is the problem of aging and ignore it.Even if they encounter  psychological problems,they can not solve the problem actively. It makes the situation worse,even carries the risk of suicide.

Objective: The main purpose of this paper is to understand the social participation,loneliness and depression of the older adults,and to analyze the relationship among the three parts.To explore whether loneliness plays an mediating role between social participation and depression.

        Methods: In this paper, Our source of data is China Health and Retirement Longitudinal Study 2015(CHARLS). A total of 8025 valid samples of people aged 60 and above are selected,describes the general characteristics of the sample,and uses Pearson and Spearman correlation to analyze the relationship between the social participation,loneliness and depression,linear regression to analyze the mediating role of loneliness,sobel method for mediating effect testing.

Results:The mean score for depression of older adults is 7.85,28.31% of them feel lonely,and 49.62% of them have social participation in daily life.Social participation is negatively correlated with depression (r=-0.096,p<0.001) and loneliness( r=-0.047,p<0.001),while loneliness is positively correlated with depression (r=0.487,p<0.001).Loneliness plays a mediating role in social participation and depression.

Conclusion: Loneliness plays an mediating role between social participation and depression,and it is helpful for the older adults to alleviate loneliness and depression and maintain a good mental state by participating in social activities.