We Crave People The Way We Crave Food

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Most people occasionally feel cravings. Meal cravings might come on suddenly for some people, or they can be triggered by the sight, smell, or mention of a certain food. For instance, viewing chocolate advertising might make you crave it. And occasionally, you might miss and crave your favorite cuisine if you haven’t had it in a while, or you might be really hungry.

On the other hand, cravings aren’t only limited to food. A new study from the Massachusetts Institute of Technology suggested that people may also crave social contact, similar to food cravings people experience when hungry. 

Since the coronavirus pandemic started in the spring, many people have only had video chats with their closest friends and family if they have seen them. According to the MIT study, our longings for food when we’re hungry and this type of social isolation have similar brain underpinnings. We review some of the study’s key results in this post to learn more about this intriguing insight into loneliness and the desire for social interaction.

Investigating The Hunger For Social Interaction

There is little research on the effects of acute required isolation, even though chronic social isolation and loneliness are linked to worsened physical and mental health. Positive social interactions could be considered fundamental human requirements, similar to other necessities like eating and sleeping.

If this is the case, the lack of pleasant social interaction could cause a desire, or “craving,” which drives behavior to make up for what is missing. Neural reward systems are activated in response to cues linked with pleasant social contact, such as smiling faces. However, the brain depiction of unmet human social demands has received little study.

To fill this gap, the researchers used a within-subject design to experimentally generate social isolation in 40 healthy, socially active young adults (ages 18 to 40, 27 women) as well as functional magnetic resonance imaging (fMRI) using a cue-induced craving (CIC) paradigm.

The new study is inspired by a recent publication by Tye, a former employee of MIT’s Picower Institute for Learning and Memory. In that study from 2016, researchers discovered a group of neurons in mice’s brains that express sensations of loneliness and cause a desire for social interaction after being alone. Studies on humans have demonstrated that a lack of social interaction can cause emotional misery, although it is unclear what neural processes underlie these emotions.

The researchers recruited healthy participants, most of whom were college students. They kept them in a windowless room on the MIT campus for ten hours where they were forbidden from using their phones to construct the strongest social isolation intervention yet attempted. 

The participants were subjected to various treatments by the researchers, and they even received training on how to enter an MRI scanner so that they could do it independently and without assistance from the researchers.

Each of the 40 volunteers performed a 10-hour fast on a different day. The participants were scanned while seeing pictures of food, pictures of people interacting, and neutral pictures like flowers after 10 hours of fasting or solitude.

The substantia nigra, a microscopic region in the midbrain that has previously been associated with drug and hunger cravings, was the focus of the researchers’ attention. The dorsal raphe nucleus, a part of the mouse brain that Tye’s lab demonstrated was active after social isolation in their 2016 study, is thought to have evolutionary ancestry with the substantia nigra.

According to the researcher’s hypothesis, the “craving signal” in the substantia nigra of socially isolated patients would be comparable to the signal generated when they saw food after a fast when they watched photographs of people engaging in social interactions.

The Findings of The Study

Based on their analysis, the researchers confirmed their hypothesis. They found that the amount of activation in the substantia nigra correlated with how strongly the patients rated their feelings of craving food or social interaction.

Additionally, the researchers discovered that people’s reactions to isolation differed according to how lonely they often were. Following 10 hours of isolation, those who had reported feeling socially isolated for months before the study’s completion had fewer needs for social engagement than those who had reported having a more active social life.

The researchers examined the striatum and the cortex as two other brain regions for activation patterns. They discovered that hunger and isolation each engaged different parts of those regions. That shows that those regions are more trained to react to particular longings, whereas the substantia nigra generates a more generic signal and can reflect a range of wants.

In sum, the study’s findings support the intuitive idea that acute isolation causes social craving, similar to how fasting causes hunger.

The study cleared the door for other studies on how social isolation impacts behavior, whether virtual social contacts like video chats might satisfy social interaction demands, and how isolation affects various age groups. The scientists also want to find out if the brain reactions they observed in this study can be used to forecast how the same volunteers will react when they are isolated during the lockdowns implemented during the early stages of the coronavirus epidemic.

Journal Reference

Tomova, L., Wang, K. L., Thompson, T., Matthews, G. A., Takahashi, A., Tye, K. M., & Saxe, R. (2020). Acute social isolation evokes midbrain craving responses similar to hunger. Nature Neuroscience, 23(12), 1597–1605. https://doi.org/10.1038/s41593-020-00742-z

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