Depression may lead to cognitive decline via social isolation

An analysis of the China Health and Retirement Longitudinal Study data found that individuals with more severe depressive symptoms tend to report higher levels of social isolation at a later time point. In turn, individuals who are more socially isolated tend to report slightly worse cognitive functioning. Analyses showed that social isolation mediates a small part of the link between depressive symptoms and worse cognitive functioning. The paper was published in the Journal of Affective Disorders.

Depression is a mental health disorder characterized by persistent sadness, loss of interest or pleasure, and feelings of hopelessness that interfere with daily functioning. It adversely affects the way a person thinks, feels, and behaves. It can lead to difficulties in work, relationships, and self-care.

People with depression may experience fatigue, changes in appetite, and sleep disturbances. Concentration and decision-making can become harder, reducing productivity and motivation. Physical symptoms such as pain, headaches, or digestive issues may also appear without clear medical causes.

Depression can diminish the ability to enjoy previously pleasurable activities, leading to social withdrawal. This isolation can worsen depressive symptoms, creating a cycle of loneliness and despair. Social isolation itself is both a risk factor for developing depression and a common consequence of it.

Study author Jia Fang and her colleagues note that depressed individuals also tend to show worse cognitive functioning. They conducted a study aiming to explore the likely causal direction underpinning the longitudinal association between depressive symptoms and cognitive decline, and a possible mediating role social isolation has in this link among Chinese adults aged 45 years and above. These authors hypothesized that social isolation mediates the association between depressive symptoms and cognitive function.

Study authors analyzed data from the China Health and Retirement Longitudinal Study (CHARLS). CHARLS is a nationally representative longitudinal survey of Chinese residents aged 45 and above. This analysis used CHARLS data from three waves in 2013, 2015, and 2018, including a total of 9,220 participants. 51.4% were women. Participants’ average age was 58 years.

The authors of the study used data on participants’ depressive symptoms (the 10-item Center for Epidemiologic Studies Depression Scale), social isolation, and cognitive function (assessed with tests of contextual memory and mental integrity). A social isolation score was calculated based on four factors: being unmarried (single, separated, divorced, or widowed), living alone, having less than weekly contact with children (in person, via phone, or email), and not participating in any social activities in the past month.

Results showed that depressive symptoms were associated with subsequent social isolation. Social isolation, in turn, was associated with subsequent worse cognitive functioning. Further analyses showed that social isolation partially mediated the link between depressive symptoms and cognitive functioning, explaining 3.1% of the total effect.

The study authors concluded that the association between depressive symptoms and cognitive function is partially mediated by social isolation. They suggest that public health initiatives targeting depressive symptoms in older adults could reduce social isolation and help maintain cognitive health in middle-aged and older adults in China.

The study sheds light on the nature of the link between depressive symptoms and cognitive functioning. However, it should be noted that the design of the study does not allow definitive causal inferences to be derived from these results. Additionally, social isolation was assessed through self-reports, leaving room for reporting bias to have affected the results. Finally, the reported mediation effect was very modest in size, indicating that the link between depression and cognitive functioning depends much more on factors other than social isolation.

The paper, “Social isolation mediates association between depressive symptoms and cognitive function: Evidence from China Health and Retirement Longitudinal Study,” was authored by Jia Fang, Wencan Cheng, Huiyuan Li, Chen Yang, Ni Zhang, Baoyi Zhang, Ye Zhang, and Meifen Zhang.