Will your brain really become dumber if you stay at home and don’t go out?

Professor Fancourt, an epidemiologist from University College London, has long been studying how social factors such as isolation affect physical and mental health. Therefore, in March of this year, when she realized that the UK was about to implement lockdown measures, she quickly recruited 70,000 participants for the study, conducting online surveys on these participants once a week to collect their physical and mental health data.

The researchers say the level of isolation people are experiencing now is unprecedented and comes with other stressors, such as fear of illness and financial strain. But it will take several years to understand what and how measures taken during the pandemic affect these risks.

“We’re seeing more and more evidence linking isolation and loneliness to increased rates of different types of illness, as well as premature death,” Fancourt says. In addition to myriad links to physical health conditions, such as obesity and cardiovascular disease, existing evidence has also demonstrated a range of possible effects on the human brain: Social isolation has been linked to an increased risk of cognitive decline and dementia, as well as mental health outcomes such as depression.

Professor Stephanie Cacioppo, a social and cognitive psychologist at the University of Chicago, said: "Since the COVID-19 pandemic, people are experiencing unprecedented isolation, accompanied by other stresses, such as economic pressure and fear of the disease. Humans are a social species and we need to rely on others for our survival."

The impact of long-term social isolation on cognition

Social isolation is closely related to our physical and mental health. A large amount of evidence shows that social isolation can cause a series of emotional disorders such as depression and anxiety, and is also closely related to obesity, cardiovascular disease and premature death. In addition, cognitive decline and increased risk of dementia are also closely related to social isolation.

In 1972, French adventurer and scientist Michel Siffre famously conducted one of the longest self-isolation experiments to date, isolating himself in a cave in Texas for 205 days.

Siffre recorded in detail the impact of the 205 days of self-isolation on his mind. He said that after a few months of self-isolation, his mind began to go blank and he had almost no thoughts. By the fifth month, his desire for companionship was so strong that he tried to make friends with mice, but was ultimately rejected by them.

This experiment uses extreme isolation (such as space shuttle crews or Antarctic researchers) to understand the psychological and cognitive effects of social deprivation. People often become anxious, irritable, depressed, etc.

However, social isolation is playing out in more insidious ways in our daily lives. For example, loneliness among the elderly. In 2019, the British Longitudinal Study on Ageing investigated the lifestyles and cognitive abilities of more than 11,000 elderly people and found that after excluding a series of interfering factors, the higher the degree of social isolation, the worse the cognitive abilities of the elderly.

Possible mechanisms affecting brain function

Neuroscientists at the Max Planck Institute for Human Development studied the brains of expedition members who went on a 14-month investigation in Antarctica and found that after 14 months of social isolation, the dentate gyrus region of the brain shrank by an average of 7%, which is closely related to human learning and memory abilities.

At the same time, the researchers also found that the levels of brain-derived neurotrophic factor (BDNF) in the blood of the expedition members were also reduced. BDNF is a protein involved in stress regulation and memory.

Like humans, mice are social animals, and social activities are important for maintaining the normal structure and function of the mouse brain.

In 2018, researchers found that mice isolated for a week were worse at distinguishing their companions than normal mice. After the mice were returned to the community for a period of time, their recognition ability returned to normal. At the same time, the researchers also found that after isolation, a signaling protein called Racl in the mouse brain was activated, which is closely related to Alzheimer's disease.

In addition, isolating animals can also cause increased levels of inflammation in animals. For example, studies on mice have shown that during solitary isolation, the inflammatory signaling factor (interleukin 6) in mice continues to increase. At the same time, similar findings have been found in human studies. A meta-analysis showed that social isolation is closely related to increased levels of C-reactive protein and fibrinogen in human blood.

Reducing loneliness and embracing society

Recognizing the potential risks of social isolation to humans, such as cognitive impairment and other health damage, many countries and health organizations have begun to seek changes. For example, some housing organizations in the United States have been committed to promoting communication among socially isolated people and promoting social participation in shared spaces.

However, for those people or social environments that cannot be changed, some scholars believe that drug treatment may be helpful. Since 2017, Professor Cacioppo's team has been committed to the study of pregnanolone to treat lonely patients. Pregnanolone has previously been found to be involved in the regulation of BDNF and various stress-related steroids, thereby helping humans reduce loneliness.

Sanofi developed a drug for schizophrenia in 1990, but it was discontinued due to lack of efficacy. Professor Zelikowsky found that in mice, this drug can effectively block Tac2 receptors, thereby alleviating people's loneliness. Professor Zelikowsky believes that this will hopefully become an effective drug for treating people with social isolation.

In addition, some researchers are also studying the effectiveness of behavioral interventions for socially isolated people. For example, a 2019 study found that frequent visits to museums, art galleries, or various exhibitions and opera performances can effectively alleviate the decline in cognitive levels of socially isolated people, regardless of the person's social participation.

Thousands of people have found themselves isolated during the pandemic, as evidenced by surveys showing that many people, especially women, have felt increasingly lonely since the pandemic began.

However, although many people feel lonely, some have found new ways to stay connected through social networks. These behaviors may provide important information about how different people cope with the impact of social separation. In this regard, Professor Fancourt said, "If we talk to people as much as possible through Skype, Zoom, etc., we may be able to offset the negative impact of isolation on us."

In addition, Fancourt said, "From a scientific perspective, this is an unprecedented opportunity to learn more about how a lack of traditional social interaction affects humans, which could change our understanding of loneliness and isolation."