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A recent study published in Biological Psychology suggests that loneliness is linked to how people perceive and process their internal bodily sensations. The findings indicate that individuals who report higher levels of loneliness tend to have less trust in their bodily signals and show reduced brain activity related to monitoring their heartbeats. This research offers a physiological perspective on why loneliness is often accompanied by heightened emotional distress.
Loneliness is commonly understood as a lack of social contact, but psychologists describe it as a state of heightened sensitivity to negative emotions and social threats. This perspective is known as the hypervigilance model of loneliness. According to this framework, lonely individuals tend to be on high alert for social rejection, which can lead to increased stress and difficulty managing emotional reactions.
“Loneliness is a significant global issue linked to various mental and physical health problems,” said study author Kentaro Ono, an assistant professor at the Center for Brain, Mind, and KANSEI Sciences Research at Hiroshima University. “In Japan, it is taken so seriously that the government has even appointed a Minister of Loneliness.”
Ono noted that his laboratory has a background in psychiatry, which led to an interest in how loneliness acts as a trigger for psychiatric disorders. “While there is a great deal of research on who is prone to loneliness and how to cope with it, the underlying mechanisms of how loneliness actually arises remain largely unknown,” Ono said.
The research team noticed that emotional isolation is frequently described in physical terms. “We noticed that people often describe loneliness through physical sensations, such as a tightening in the chest or a sinking feeling,” Ono said. “Our lab was already investigating ‘interoception’, which is the perception of our internal bodily states. Therefore, we were motivated to bridge this gap by exploring the relationship between loneliness and interoception, hoping to better understand how these emotional struggles physically manifest in the body.”
Emotion regulation depends heavily on this process of interoception. Psychologists divide interoception into different categories to better understand how it works. Interoceptive accuracy refers to how well a person can physically detect internal signals, such as a racing heart. Interoceptive sensibility describes a person’s subjective beliefs about their bodily sensations, including whether they view these physical responses as trustworthy or distressing.
Previous research hints that interoceptive sensibility plays a role in how well people manage negative feelings. Brain regions involved in cognitive control, such as the dorsolateral prefrontal cortex, are also known to help process bodily signals. This area of the brain helps integrate physical sensations with emotional meaning to regulate distress.
To measure this brain-body connection, scientists often look at the heartbeat-evoked potential. This is a specific pattern of electrical brain activity that occurs in response to each individual heartbeat. Researchers designed the current study to explore whether loneliness is associated with differences in interoceptive accuracy, interoceptive sensibility, and heartbeat-evoked brain activity.
The scientists recruited 45 healthy university students between the ages of 18 and 25. Six participants were later excluded due to issues with data quality, leaving a final sample of 39 participants. Participants first completed a series of questionnaires. These included the UCLA Loneliness Scale to measure subjective feelings of isolation, the Multidimensional Assessment of Interoceptive Awareness (MAIA) to gauge interoceptive sensibility, and a standard inventory to assess depressive symptoms.
Next, the participants completed two behavioral tasks to measure their interoceptive accuracy. In a heartbeat counting task, they were asked to silently count their heartbeats over various time intervals ranging from 25 to 50 seconds without checking their pulse. In a heartbeat discrimination task, they listened to a series of tones and had to judge whether the sounds were in sync with their own physical heartbeats or delayed.
Finally, the researchers recorded the participants’ brain and heart activity. Participants sat in a quiet, dimly lit room for three minutes while the researchers collected continuous electroencephalogram (EEG) and electrocardiogram (ECG) recordings. EEG uses sensors on the scalp to measure electrical brain waves, and ECG measures the electrical activity of the heart. The researchers used these concurrent recordings to extract the heartbeat-evoked potential, allowing them to see how the brain responded to cardiac events.
The average loneliness score in the sample was 40.5 out of a possible 80 points, indicating a moderate level of loneliness among the students. The survey findings indicated that higher loneliness scores correlated with specific aspects of interoceptive sensibility. People who felt more lonely tended to report more worry about their bodily sensations. They also reported lower emotional awareness, less ability to use bodily sensations to regulate distress, and less trust in their bodies as a safe resource.
“We were quite surprised, and ultimately reassured, by the specific patterns in our survey data,” Ono told PsyPost. He noted that the MAIA questionnaire measures interoceptive sensibility across several different categories. “We found a strong correlation between the UCLA Loneliness Scale and one specific category of MAIA: the one reflecting how people think about or appraise their bodily states. Seeing the correlation clearly localized to this specific category, rather than being broadly scattered across all categories, gave us a lot of confidence in the reliability of our data.”
Loneliness was not associated with interoceptive accuracy. Participants with higher loneliness scores were just as capable of accurately counting their heartbeats and distinguishing synchronized tones as those with lower scores. Heart rate variability, a physiological measure of the changes in time intervals between consecutive heartbeats, also showed no statistical relationship with loneliness.
When looking at the EEG recordings, the researchers found an association between loneliness and the brain’s processing of cardiac signals. Higher loneliness scores were associated with a reduced electrical brain response to heartbeats over the left frontal areas of the scalp. Using specialized source localization software, the scientists traced this reduced electrical activity to the left dorsolateral prefrontal cortex, which is a brain region typically involved in higher-order cognitive control and emotion regulation.
To ensure these brain activity patterns were linked to loneliness rather than other factors, the researchers ran additional statistical models. The association between loneliness and reduced brain responses to heartbeats remained present even after the researchers controlled for the participants’ age, sex, and severity of depressive symptoms. This provides evidence that the observed physiological differences relate specifically to the experience of loneliness rather than general depression.
“The most important takeaway is that the brain and the body are in constant communication, and changes in your bodily state impact your mental state,” Ono said. “Therefore, paying attention and taking care of your physical body is crucial for your emotional well-being.”
Ono added that these findings support the idea that social connection helps people regulate their physical responses. “In our study, we interpret that individuals with low levels of loneliness have brains that successfully detect bodily changes triggered by isolating situations, allowing them to effectively regulate and correct their bodily states,” Ono explained. “Conversely, individuals with high levels of loneliness tend to ignore or not worry about these altered physical states.”
“Because they fail to attend to and adjust their physical response to isolation, they may fall deeper into loneliness,” Ono noted. “Based on this, we suggest that practices which help you deliberately direct attention to your body, such as yoga or mindfulness meditation, could be effective methods for alleviating loneliness.”
The study relies on a cross-sectional design, meaning the researchers measured all variables at a single point in time. Because of this design, it is impossible to determine the direction of the relationship. Reduced brain processing of bodily signals might contribute to feelings of loneliness, or chronic social disconnection might lead to changes in how the brain handles internal sensations.
“One important caveat is that our current study had a relatively small sample size of about 40 participants,” Ono said. “Because of this, we must be careful not to overstate the strength of these effects just yet.”
This small sample of university students generally reported moderate loneliness, meaning the findings might not apply to older adults or individuals experiencing severe, chronic social isolation. The study also recorded brain activity during a resting state rather than during an active emotional task. This limits the ability to tie the brain activity patterns directly to active emotion regulation in real-time social situations.
The use of EEG to track the source of brain activity has spatial limitations compared to other imaging techniques. Although the data points to the left dorsolateral prefrontal cortex, EEG sensors on the scalp provide only an approximation of where electrical signals originate in the brain. “To draw firmer, more generalized conclusions, we are already planning a much larger-scale study to further investigate this relationship between loneliness and interoception,” Ono added.
“Moving forward, we are very interested in whether we can predict an individual’s future vulnerability to loneliness,” Ono said. “For example, entering university is a major environmental shift where many students face isolating situations.”
“If we can use these findings to screen for individuals who are highly susceptible to loneliness during such transitions, we might be able to design and implement much more effective, preventative interventions.”
The study, “Loneliness is associated with altered interoceptive appraisal and attenuated prefrontal heartbeat-evoked potentials,” was authored by Kentaro Ono, Takafumi Sasaoka, and Shigeto Yamawaki.