The Neuroscience Of Homelessness


A black and white drawing depicting a homeless man in a winter coat with a blanket in lap, a plastic cup with change in it in front of him, seen from ground level perspective seated against a wall. In the foreground, people walk by, with only their legs in the field of vision. A can is littered in the street. A black and white drawing.

The same scene as in Piece 1, but from the perspective of the homeless man. The cup is in the center foreground, and a mirror of the people walking by is shown. Among other cars in the street in the background, a Columbia bus drives by. A black and white drawing.


Every night, half a million people in the United States sleep in inadequate housing, with about two-thirds staying in temporary shelters and one-third being completely unhoused [1]. Of those half million, an estimated 76.2 percent have at least one diagnosable mental disorder [2]. Mental health disorders, especially substance abuse disorders, are widely known to be prevalent in communities of unhoused people, but the distinct interactions between homelessness, substance abuse, and the social conditions they exist in are not completely understood. How could a diverse population of over half a million people, having only a lack of consistent housing in common, be so disproportionately impacted by mental health disorders? Isolation, substance abuse disorders, and the large-scale societal rejection of their humanity work together to lead to severe psychological damage over time. While exploring the concept of homelessness, this article uses terms such as “unhoused people,” “people without homes,” and “people experiencing homelessness” interchangeably to avoid the stigma associated with the term “homeless” [3]. This is not to diminish the pain many such individuals live through, but rather to prevent further dehumanization already associated with this marginalized population [3].


One particular source of psychological trauma that unhoused people must grapple with in their day-to-day lives is having incredibly limited social networks, which are the connections that one can consistently seek support from, such as family and friends [4, 5]. Such limited social networks can lead to extreme isolation and loneliness. Loneliness has been shown to have a significant association with psychoses, suicide, and depressive symptoms [6]. This social isolation can be attributed to three major factors: members of their network dying, members being pushed away or removing themselves from the network, and/or members having too many problems of their own to engage in the network [7]. Furthermore, in one study on the social networks of unhoused and precariously housed people in Vancouver, 116 participants were excluded from the study due to not having a single positive social network connection, leaving only 60 participants, of which the average number of people in their networks were 2.57 [5]. This level of solitude is consistent with the findings of other studies on the subject [4, 8]. Social networks also have a direct impact on physical health, including increased risk of mortality; the increased longevity associated with having adequate social connections is comparable to quitting smoking and decreases the chance of physical diseases such as stroke and heart disease [9, 10]. Because people living through homelessness are often so detached from those around them, their mental and physical health may be compromised.


This isolation has been shown to have a direct impact on the brain by affecting the amygdala, a small collection of nuclei in the temporal lobe that is widely known to be the fear control center of the brain [5]. Beyond that, it is associated with social behaviors, decision-making processes, and the development of substance abuse disorders [5]. More complex social networks have been shown to correlate with larger amygdala volumes [11]. A study conducted to investigate the role of social behavior in rats found that rats raised in isolation have smaller amygdala volumes compared to socially raised rats [12]. This difference in size has been shown to affect their ability to display sexual behaviors, demonstrating that the volume of the amygdala affects social behavior [12]. Thus, it is possible that the isolation of many unhoused individuals may be associated with a reduced amygdala size not only in rats but also in humans [5]. In fact, a recent study on unhoused individuals observed that those with larger social networks had significantly larger amygdalae and central nuclei volumes as compared to those with fewer connections. This reduced amygdala size may lead to abnormal social behaviors and further mental illness, contributing to a cycle of solitude [5].



Hands cupped together, holding sand which is streaming

slowly through the fingers. A black and white realism digital drawing.

Hands cupped together, holding sand which is streaming slowly through the fingers. A black and white realism digital drawing.

Loneliness can also increase the likelihood of developing and maintaining substance abuse disorders, further damaging the amygdala [13]. Those lacking substantial support systems may feel the need to compensate through substance use, and because the social environments of the most unhoused people are so sparse, it can make recovery more difficult [14, 15]. One particularly prevalent substance of abuse is alcohol. An estimated 36.7 percent of people living through homelessness have alcohol abuse disorders at any given moment, compared to an average rate of 14 to 15 percent in the United States [2, 16, 17]. Alcohol abuse is the most common mental health disorder in populations of people living through homelessness and for the purposes of this article, will be used as a model for substance abuse [2]. When alcohol enters the brain, it affects the ability of neurons to communicate [18]. Neurons use neurotransmitters to communicate with each other, and neurotransmitters are recognized when they bind to receptors along a neuron's surface. Alcohol essentially numbs the brain by enhancing inhibitory receptors, making it more difficult for electrical signals to be transmitted. If alcohol is consumed repeatedly and for a prolonged period of time, the brain compensates for this numbing by becoming hyperexcitable to maintain a more neutral status even when alcohol is present [18].


During alcohol detoxification, a process characterized by cessation of alcohol use in individuals with alcohol dependence, the brain begins to send far more electrical signals than it should because of its hyperexcitability [18]. In extreme cases, this can manifest in anxiety, auditory and visual hallucinations, delirium, and seizures that involve involuntary muscle spasms and loss of consciousness [18]. Delirium tremens is the most serious complication of alcohol withdrawal, symptoms of which include those previously mentioned along with extreme confusion and cardiovascular failure, among others [17]. For those who develop delirium tremens, only one to four percent will die if the condition is treated. If untreated, however, mortality can reach 35 percent, which is concerning given that treatment is often inaccessible for many people living through homelessness [17]. Those with substance abuse disorders and no access to treatments understandably may want to avoid these symptoms because they are at risk of mortality if they do not continue using. Furthermore, through repeated detoxifications, cravings become more powerful and symptoms get worse, increasing the likelihood of seizures [18, 19]. There is evidence that repeated detoxifications lead to loss of brain tissue associated with control of behavior, and impairments to proper emotional responses due to changes in the connectivity of the insula, a structure involved in emotion and consciousness [16]. Thus, those who are dependent on alcohol but lack consistent access to it may experience repeated cycles of use and detoxification, not because they're trying to quit but simply because they don't have the available income to afford it. Hence, they undergo numerous cycles of forced detoxification which most likely increase their chances of relapse and brain damage [16, 18] . So if a person living through homelessness spends what little money they have on substances, they might be doing so to avoid abrupt withdrawals and avert serious health consequences .


This repeated cycle of substance use and detoxification illustrates the self-perpetuating trauma of isolation and substance abuse experienced by those without homes, both of which can lead to mental illnesses. To add to this physiological threat, isolation and substance abuse contribute to the negative social perceptions commonly held against people without homes. People in the U.S. tend to have significantly more negative views of those with substance abuse disorders, housed or unhoused, as compared to those with other mental health disorders [20]. This may be due to a perception that substance abuse disorders develop due to moral shortcomings, in conjunction with false assumptions of potential hostility [20].


An anatomical drawing of the brain, with various parts mentioned in written label. These include the cortex, amygdala, hypothalamus,

An anatomical drawing of the brain, with various parts mentioned in written label. These include the cortex, amygdala, hypothalamus.


This prejudice against individuals with substance abuse disorder can be physically seen in brain scans showing the activation of certain regions of the brain. Susan Fiske, a professor of psychology at Princeton University, developed a schematic for how people perceive and categorize others, known as the stereotype content model [21]. Fiske’s model categorizes people’s perceptions of others by assigning them a location along two axes: warmth and competence [21]. Warmth is a determination of whether a person poses a threat or is friendly, and competence is how able they are to act on that intent [22]. While groups that are seen as warm and competent evoke positive emotions, like pride, groups that are categorized as not warm and incompetent elicit the opposite reaction [22]. Such groups include people without homes and people with substance abuse disorders, and they tend to evoke feelings of contempt, fear, and disgust [23]. In 2006, Fiske and fellow Princeton University researcher Lasana Harris examined the brains of 10 participants when viewing photographs of various objects and social groups [23]. They found that, when viewing these negatively perceived groups, the amygdala and the insula—the structures in the brain responsible for fear response and emotional processing—had responses consistent with the neural signature seen in disgust and fear [23].



Furthermore, they found that the medial prefrontal cortex, a region of the brain activated by social engagement, had a significant decrease of activation when viewing groups perceived as incompetent and not warm compared to other social groups [23, 24]. This indicates a dehumanization of individuals experiencing homelessness on a neural level, as the typical patterns of brain activity seen in usual social cognition are absent when viewing groups considered cold and incompetent [23]. In fact, these neural patterns were similar to viewing an object [23]. Perceiving unhoused people as incompetent, inherently harmful, and potentially less than human makes it much more difficult to produce the sociological changes necessary to decrease the unwaning population of individuals living through homelessness [1]. Without change to this perception, discrimination against those without homes will persist.


In a poll of 541 American adults across 47 states, 62.1 percent of respondents thought that irresponsible behavior from unhoused people led to their situation, and 41.7 percent thought that laziness also played a part [25]. In reality, the reasons behind homelessness are incredibly complex and include many systemic and personal factors out of an individual’s control. Major systemic facets include the economic conditions in the place one lives, social safety nets, and access to affordable housing [26]. Personal factors include trauma at a young age, incarceration (which could also be considered systemic), and severed relationships, especially familial ones [26]. Disadvantaged people who have experienced a combination of factors that put them at high risk of homelessness often lack necessary support systems to avoid homelessness, and once unhoused, they struggle to escape from it permanently [27, 28]. Homelessness is a sociological issue in addition to a neurological one, but both approaches must be considered to improve the social safety net and how we treat psychiatric illnesses.


Housing should be considered a human right in the United States, and everyone should be guaranteed it. However, even if such a systemic change were too radical, we must utilize the fact that two-thirds of the homeless population in the United States are in temporary shelters and provide them with psychiatric care [1]. This would be a massive step in the right direction to ending the cyclic nature of homelessness. Isolation may change the structure of the brain, contributing to mental illness and substance abuse [5, 12]. These can lead to even more neurological maladaptations, in turn causing more isolation [5, 11, 12]. Because poverty facilitates repeated cycles of detoxification, all these conditions may worsen over time [16, 18, 19].


The same scene as in Piece 1, but from the perspective of the homeless man. The cup is in the center foreground, and a mirror of the people walking by is shown. Among other cars in the street in the background, a Columbia bus drives by. A black and white drawing.

A black and white drawing depicting a homeless man in a winter coat with a blanket in lap, a plastic cup with change in it in front of him, seen from ground level perspective seated against a wall. In the foreground, people walk by, with only their legs in the field of vision. A can is littered in the street. A black and white drawing.


The mental illnesses associated with homelessness can be treated much more effectively than they currently are. Given that among unhoused people, 12.4 percent have schizophrenia spectrum disorders, 25.4 percent have a lifetime personality disorder, and 4.1 percent have bipolar disorder, just to name a few, treating each condition individually is ineffective [2]. Using integrated treatment models, where each of the conditions affecting an individual are considered holistically rather than in isolation, may lead to far better outcomes, especially when one of the conditions is substance abuse [29]. Furthermore, supportive housing, which consistently outperforms conventional temporary housing, especially for those with mental illnesses, has not been studied nearly enough due to a lack of urgency from the general population for the government to fund it [30]. Such programs need more financial support, more robust studies and analysis, and more widespread implementation.


People living through homelessness include some of the most vulnerable and disadvantaged people in our society: people of low socioeconomic standing, some carrying trauma from an early age, some abandoned by their families, and many with mental illnesses. While it may not seem like there is much for a single individual to do, the first steps are changing attitudes, recognizing biases, and donating to local support organizations. 70 percent of Americans already support increased federal funds dedicated to homeless populations, so all it would take to enact change is greater vocality on the topic [25]. In order to bring about public policies that would involve integrated psychiatric supportive care at housing facilities, public perception of people living through homelessness must change first. By finally validating the suffering that unhoused people go through, people will realize that housing should be a right for all!



Works Cited


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