A lone person stands amid a bustling crowd of familiar faces. A glance around at the wide, inviting smiles on the faces of their family and friends should spark the warmth of happiness, but a different feeling bubbles inside. Painful and crushing, the feeling turns the surrounding joyous laughter into a condescending mockery and damages the connection to that warmth. This feeling is loneliness. Loneliness affects 80 percent of minors and 40 percent of seniors [1]. While it is widespread, its effects are not well understood, and any potential solutions are complex. Understanding the detrimental impacts of chronic loneliness in humans is especially essential in our socially connected world where loneliness is more prevalent than ever. We can better understand the neurological impact of loneliness by examining its evolutionary roots.

Loneliness is the discrepancy between a person’s preferred and actual social conditions; it may increase the chances of survival of a social species because it informs when social needs have not been satisfied [2]. Like how hunger warns us about low glucose levels in the body, loneliness warns us when our social demands have not been met. Animals do not experience loneliness as humans do; instead they experience a self-preservative mechanism known as social loss. Generally, an animal’s preferred social condition consists of an attentive parent and a large selection of mates. If their living standards do not meet these criteria, this creates a negative discrepancy between their actual situation and preferred standards, appropriately called social loss [2].

When outside of a group, animals need to work harder to protect themselves from harm. For instance, when fish swim in large schools, each individual fish’s chance of being preyed upon by external threats decreases [3]. However, even though fish that swim towards the outside of the group may not necessarily be weaker or slower than the other fish, being further away from the center of the group increases their vulnerability and decreases their survivability, therein causing the separated fish to experience social loss [3]. Social loss will act as a cue for the animal to return to the protective group to keep them safe and subsequently reduce their social loss. Without the advantages of mutual protection provided by a group, social animals experience increased feelings of anxiety [4]. This is sparked by interactions between different parts of the brain; the increasing interactions between the hypothalamus, pituitary gland, and adrenal gland raise an animal’s stress levels to increase their awareness and protect them from predation. Their increased stress levels result in interrupted sleep, which decreases the chance for a predator to attack a solitary animal when it is sleeping. Additionally, an increase in vascular activity underpins the instinctual fight-or-flight response in stressful situations. The stress response to social loss is thought to be an adaptive mechanism that acts as a cue for the animal to seek out protection and interaction from a group.

In most cases, the effects caused by social loss have net benefits for animals: the long-term benefits of survival outweigh the short-term costs from the anxiety of being separated. On the contrary, in humans, chronic loneliness is often detrimental and harder to study. Studying the effects of social loss in non-human animals has provided us with an understanding of the basic biological phenomena associated with loneliness, such as increased stress and anxiety. However, animals cannot express their internal emotions like humans can, so studying animals only provides what is externally, objectively observable. To study the internal, subjective state of loneliness in humans, scientists need a tangible way to identify signs of loneliness. If somebody is happy, for example, a scientist may record how many times they smile or laugh, or how much of serotonin is released. When studying loneliness, scientists use both objective and subjective social exclusion to make these measurements. Objective social exclusion is when someone is physically alone. In contrast, subjective social exclusion, or loneliness, occurs when someone believes they are alone, even though they may not physically be. Manipulating objective social exclusion to incite subjective social exclusion allows scientists to discernibly study the effects manifested from a human experiencing loneliness.

Studying loneliness in humans has allowed scientists to pinpoint specific brain regions associated with loneliness. Dr. Katherine Powers, a psychology professor at Harvard University, found that the dorsomedial prefrontal cortex (dmPFC) is more active in people that feel socially included; the dmPFC is a region of the brain used to make sense of social knowledge. Dr. Powers manipulated objective social exclusion to create subjective social exclusion by convincing participants that they would feel lonely in the future. Participants were randomly assigned into groups and told they would be either be socially excluded or included and gave them personality tests [5]. Participants were told whether or not they would have stable relationships in the future, ostensibly based on their personality tests. Powers hypothesized that individuals that felt excluded would respond positively to scenes like potential social acceptance and negatively to more social exclusion.

Participants were then shown images of people with positive, negative, or neutral levels of sociability while their brains were scanned using fMRI. When the people grouped as socially excluded viewed negative social scenes, their dmPFC activity was low. In contrast, the socially included participants demonstrated higher dmPFC activity to all types of scenes [5]. The dmPFC activity increased in both socially included and excluded individuals as the scenes increased in their sociability. However, in all cases, the dmPFC activity in socially excluded individuals were simply lower. Lower dmPFC activity in general in socially excluded people may mean that they will find it harder to reach out to people or develop a strong connection with someone to combat loneliness as compared to socially included people. Scientists manipulating objective social exclusion, through describing the subject’s social status in the future to achieve subjective social exclusion, can mimic feelings of loneliness. However, the anticipation might not be a true reflection of the neurological impacts on an individual who is actually experiencing subjective social exclusion. While there are potential complications from this study, it still provides insight into the difference in neuroanatomy caused by loneliness.

Socially excluded individuals find it harder to form more meaningful connections than socially included individuals, which is especially concerning when considering the long-term effects associated with loneliness. Loneliness is correlated with numerous personality disorders, cognitive decline, and depressive symptoms [1]. To study the correlation between loneliness and major depressive disorder (MDD), Dr. Mark van Winkel, a psychologist at the Maastricht University, used self-reporting techniques to hopefully understand the patterns of how a lonely individual might develop the disorder. In the experiment, participants diagnosed with MDD wore a digital wristwatch that would emit a total of 50 beeps randomly between 7:30 a.m. and 10:30 p.m. [6]. After each beep, participants filled out a self-assessment sheet that asked three questions about whether they were physically alone or with company, how much they enjoyed the company they may have been with, and whether they felt lonely. Through five consecutive days, whenever the wristband would beep, participants would self-report their answers on a seven-point rating scale. Van Winkel discovered that, after a self-assessment in which the participant felt lonely, they were more likely to answer that they did not enjoy the company they had or were more likely to be alone on the next self-assessment. Participants were more likely to withdraw socially and view others more negatively after feeling lonely. This transition from momentary to long-term loneliness is tied to having negative social experiences and therein feeling more loneliness, creating a positive feedback loop [6]. By highlighting patterns of loneliness in a person’s daily life, Van Winkel illustrates the disadvantages that socially excluded people have in feeling lonely more often. This downwards trajectory for lonely individuals could lead to lower and lower activation of the dmPFC, resultantly perpetuating feelings of stress, fear, anxiety, and anger, all while diminishing self-esteem and the desire to develop strong bonds [1]. However, the path down to chronic loneliness can be disrupted with intervention.

To steer people away from the path leading to chronic loneliness, there are four methods that have been used: social support and mentorship, socialization opportunities, social skills, and therapy [7]. One method focuses on social support and mentorship. Andy Dickens, a research fellow at the University of Birmingham, conducted a study to evaluate the effectiveness of a mentoring service on socially isolated older people. These people were provided professional help and advising and the researchers measured the participants’ wellbeing over the course of six months using a mental health score, a physical health score, a depression score, and scientific surveys [8]. The study aimed to examine the effectiveness of mentoring intervention compared to usual care; however, Dickens found that there was no statistically significant evidence suggesting that mentoring was more effective than normal care [8]. Although the individuals were getting help for their loneliness, this does not fulfill a lonely individual’s need for two-way connections. Since the study focused on a one-sided professional relationship, the older people could not give back their support and their loneliness stemming from the lack of connection could not be fulfilled.

Another method simply calls for increased opportunities for socialization, and the advent of social media and globalization has made this more achievable. Despite the fact that this is true, people are more lonely than ever. The increase of opportunities does not always cater to the needs of a lonely individual. A lonely individual might be surrounded by a lot of people and have numerous opportunities but still feel like they do not want to reach out [7]. A third method suggests that teaching lonely people social skills will make their socializing easier. Some programs could include training people on their conversational ability or interpretation of body language [9]. Though this does seem promising since, as Van Winkel’s study suggests, there might be a decline in social skills. However, this method will not be effective if the main cause of someone’s loneliness is not their lack of skills. Finally, the fourth method is through cognitive behavioral therapy (CBT), where individuals are taught to identify their automatic negative thoughts and reflect on them. The goal of CBT is to change an individual’s thinking. Participants answered questions about their disconnection with others using a scale of one to four and showed varying results of the significance of CBT on reducing loneliness as well. The results did not show strong statistical significance for a solid conclusion to be derived [9]. Since different interventions yield mixed results this suggests that loneliness is a unique emotion that must be treated differently based on individual experience.

Loneliness is a complex emotion, and modern scientific studies have reformed our perspective as to how to diagnose and treat it. Current research emphasizes the need for doctors to be careful with misdiagnosing loneliness for other mental illnesses. Often in clinical settings, symptoms of loneliness are mistaken for other mental illnesses, and an individual that needs an intervention for loneliness will receive unsuitable help. Due to our increased understanding of the symptoms and neurological activity accompanying loneliness, these misdiagnoses can be reduced and chronically lonely individuals may be able to get more suitable treatments. Attention brought to such an enigmatic topic is critical, especially when the number of people that feel lonely keep increasing. The advancements of technology and our rapidly developing world means that information about loneliness can be shared from expert to expert, building on research until we can determine solid methods of intervention against it. Chronic loneliness is establishing itself as a contemporary problem, but modern approaches are slowly being devised to stop that bubbling feeling from the inside before it grows into something more.


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