A Slippery Slope to Depression

As many as 40 per cent of middle-aged and elderly adults may suffer from chronic loneliness, meaning there is a discrepancy between their preferred and actual social relations. That puts them at risk for depression. But what is the mechanism that links the two? Professor Tatia Mei-chun Lee, Chair Professor of Psychological Science and Clinical Psychology and May Professor in Neuropsychology, is a pioneer in researching the problem of loneliness in Chinese populations from behavioural and neuroscience perspectives, with the hope of finding a pathway for helping sufferers.

Working with local, national, and international collaborators, Professor Lee has been studying the patterns in the brain related to loneliness and how these interlink with depression, rumination, and higher cognitive functions.

“I became interested in loneliness because number one, it is a significant threat to mental health. And number two, because people now live longer and the risk of feeling lonely also increases,” she said.

Her team’s first major study, published in 2016, identified a neural network in the brain associated with feelings of loneliness. Subjects underwent a functional magnetic resonance imaging (fMRI) scan to look at their brain in a resting state and in response to affective pictures. They also completed a standard loneliness survey to measure their perceived loneliness.

The results showed weaker structural connectivity between key parts of the brain among those who reported feeling lonely. They also had stronger brain activity in response to negative emotional images, suggesting loneliness facilitated hypervigilance to emotions that posed a social threat.

Depleted resources

Professor Lee noted that while the brain typically changes in response to experience, “rarely has this been shown in relation to an intangible experience like loneliness. Feeling lonely leaves marks on the brain.”

She also did a study showing how loneliness and late-life depression interact in the brain. The number of depressive episodes was found to increase when a person’s perceived loneliness increased. Initially, that increase activated the striatum in the brain – a neural region responsible for reward sensitivity and reward learning. However, after multiple depressive episodes, this activation decreased.

Professor Lee’s explanation is that with the first depressive episodes, the brain may work hard to compensate. “It may be that after repeated depressive episodes, their resources become depleted. That’s why there’s a changing relationship. This is our speculation.”

She and her team have also looked at how cognitive status and higher cognitive functions are affected when depressed people feel lonely. Unsurprisingly, there is a negative impact. However, Professor Lee’s team member, Professor Robin Shao Zhengxi, Assistant Professor (Research), was able to tease out the different impacts of depression and loneliness.

Among middle-aged adults performing a cognitive task measuring executive control functions, depression was associated with more errors, while loneliness was associated with faster response time, showing that depression and loneliness impact executive control functions in different ways. Correspondingly, depression and loneliness were also associated with opposite patterns of brain functional connectivity during task performance.

“The better executive control performance and stronger functional connectivity of the high loneliness individual may imply enhanced top-down cognitive control. Maybe they are using that to try to regulate the very uncomfortable feeling of loneliness. But when they do that in the long term, this upregulation might lead to exhaustion of high-level cognitive resources, and the person may then develop a mood disorder,” Professor Lee said, adding that this, too, was speculation.

Other risks and possible remedies

Professor Lee has also found that loneliness can interact with rumination to exacerbate depression. While negative rumination, or brooding, is known to be associated with depression, her research showed that it is of greatest risk when a person ruminates on being lonely. Another known depression risk factor – childhood experience of emotional neglect – was also found to be mediated through loneliness.

Explaining the neural effects of loneliness is not Professor Lee’s only interest. She has also been looking at how to mitigate the problem. One project used a specially designed, eight-week meditation training programme and found a significant cause-and-effect relationship, with participants less affected by emotional stimuli after the training. She is also leading a Collaborative Research Fund project on psychological resilience, which relates to how quickly one can recover from psychological challenges and trauma, and how resilience relates to mental health.

“We study loneliness to understand how it impacts neural functions and our behaviours so we can then look at how to manage it and promote well-being. We know loneliness is a high-risk factor, so if we can do something to reduce it, it will lower the risk of developing mental health problems,” she said.