Being homeless has a profound effect on health. Homeless patients have higher rates of chronic illness, morbidity, and mortality than patients who have stable housing.^{1,2,3,4,5,6,7} Lacking insurance and transportation, their access to care is limited. Obtaining food and shelter are higher priorities for the homeless person than seeking health care.^8,9 Homeless patients present for medical attention later in the course of their illness.^10,11 Comorbid conditions such as mental illness and substance use can complicate adherence to treatment plans. Furthermore, providers often do not incorporate the challenges faced by homeless patients into management plans. This chapter explores the relevance of homelessness to health and health care and presents strategies to improve the care that homeless patients receive.

In the United States in 2013, a total of 610,042 individuals were homeless on a single night and an estimated 2.5–3 million people experienced homelessness over the course of the year.¹² Over one-third of individuals experiencing homelessness are persons in families and one-fourth of all Americans who are homeless are children.¹³ The median age of the homeless population is rising at a rate faster than that of the general population; the median age of homeless adults is now approximately 50 years.¹⁴ This rise in the age of this population is thought to be attributable to a cohort effect: individuals born in the second half of the baby boom (1954–1965) have had an elevated risk of homelessness throughout their lives.¹⁵ There is concern for another cohort effect, among those born in the 1990s.¹⁶

The most commonly accepted definition of homelessness in the United States is from the Homeless Emergency Assistance and Rapid Transition to Housing (HEARTH) Act of 2009.¹⁷ The HEARTH Act updates the original Federal definition, the McKinney Act of 1987.¹⁸ The HEARTH Act defines a homeless individual as:

The HEARTH Act also includes individuals or families who will imminently lose their primary nighttime residence within 14 days and lacks resources or support to obtain permanent housing and those who are fleeing or attempting to flee interpersonal violence. It has a more expansive definition for homelessness for unaccompanied youth younger than 25 years or homeless families that includes those with severe residential instability and chronic disabilities or barriers to employment.

The chronically homeless person is defined by the Department of Housing and Urban Development as someone who has been homeless for at least 1 year or has had four episodes in a 3-year period and who has a chronic, disabling condition. Chronically homeless persons face multiple barriers to finding stable housing and employment. Although approximately 20% of people who experience an episode of homelessness are chronically homeless, approximately 50% of persons who are homeless at any point could be considered chronically homeless.¹⁹ Chronically homeless individuals are more likely to be single men and have substance use and mental health problems. The intermittently homeless person is someone who has had multiple, short, self-limited episodes of homelessness. Most have spent time living with friends or family prior to losing their housing. Intermittently homeless people regain housing, but tend to be precariously housed; thus, they are at high risk of becoming homeless again. Typically, intermittently homeless persons have low income, low educational attainment, and may be escaping violent situations within their own homes. The prototypical intermittently homeless person is that of a member of a female-headed household that is struggling financially to get by.

The in-crisis homeless person is someone who has had one episode of homelessness brought about by a major crisis: an economic, health-related, or natural disaster (fire, earthquake). In general, those with crisis homelessness regain their housing and do not lose it again.

Unaccompanied youth, as opposed to homeless children living in families, are adolescents or young adults (up to 25 years old), living on their own without parents. These youth have often fled abusive situations or family disapproval caused by conflicts over their sexual identity. This population is marked by high rates of substance use, survival sex (exchanging sex for money, drugs, or housing), suicide, and transience, with high rates of movement between different cities. Another group of unaccompanied youth is those who have aged out of the child welfare system. Every year, 30,000 youth aged 16 and older age out of the system. Studies have shown that over a third of these youth experience homelessness by the age of 26.²⁰ A significant number of young women who do so are pregnant or parenting.

Although many of the necessary adjustments in providing health care are similar across the patterns of homelessness, each group presents unique needs and challenges.

Many people, health-care providers included, do not consider homelessness a medical problem. Reviewing the complex causes and risks of homelessness, however, helps providers understand ways to intervene to prevent homelessness, mitigate its risks, and address medical issues. As homelessness worsens health, understanding the challenges faced by homeless individuals is essential to providing effective medical care.

CAUSES AND RISK FACTORS FOR HOMELESSNESS

The causes of homelessness are disputed. Some emphasize personal vulnerabilities (e.g., mental illness, substance abuse), and others cite systemic and structural problems (e.g., poverty, lack of affordable housing), as the root causes.¹³ Homelessness can be conceptualized as resulting from a complex interaction of protective and risk factors occurring in the context of poverty and little access to housing (Table 28-1). While the primary risk factor for homelessness is poverty, health factors, including chronic illnesses and mental health and substance use problems, make individuals more vulnerable to homelessness. Intervening to mitigate the risks and bolster the protective factors may have a profound effect on health.

Personal Vulnerabilities

Poverty is the most essential personal and social vulnerability leading to homelessness, but it is not the sole determinant. Other personal vulnerabilities include childhood and adult victimization, and “out of home” experiences as a child (e.g., involvement in the foster care system, being homeless as a child, being in the juvenile justice system, being a runaway or “throwaway” child).^21,22 Many persons leaving state or federal prisons become homeless at discharge.

Structural Factors

Important structural factors include the availability of jobs that pay enough to allow people to maintain housing (and meet other basic needs) and the presence of affordable housing for low-income individuals. Social programs can be part of the “safety net” that prevents people from becoming homeless. Programs such as social insurance (Temporary Assistance to Needy Families, Social Security Disability Income, and county general assistance and unemployment insurance), rent subsidies (Section 8 vouchers), temporary housing, medical care, psychiatric care, and substance use treatment to low-income individuals can mitigate the effects of forces precipitating homelessness.

In an environment with limited low-cost housing and employment opportunities and an inadequate safety net, those lacking personal resources may become homeless; as the safety net erodes and the economy worsens, those with less vulnerability also may find themselves to be homeless.

HEALTH STATUS OF HOMELESS POPULATIONS

Homelessness is a concern for medical providers because not only can it be precipitated by medical problems, but also it puts people at risk for illness. Homeless people often are homeless because they are ill and ill because they are homeless.

Homeless persons have high rates of morbidity and mortality. More than one-third of all homeless persons report their health as fair or poor. In comparison, only approximately 11% of the population at large and slightly less than one-fourth of those individuals who live in poverty feel this way about their health.^10,23

Homeless people have high rates of both acute and chronic illness. Homeless patients are more likely to contract communicable diseases such as tuberculosis,²⁴ and have higher rates of human immunodeficiency virus (HIV) infection and viral hepatitis because of the increased likelihood of unprotected sex and injection drug use.²⁵ Foot problems from walking in ill-fitting shoes, swollen legs, and poor dentition are other common problems. Rates of chronic illness are higher than in non-homeless cohorts, and can be challenging to manage, given limited access to health services, competing priorities, and barriers to disease management.

Homelessness puts women and children at particular risk for poor health.²⁶ Many women become homeless during pregnancy. Homelessness, in turn, puts them at risk for complicated pregnancies. Homeless women are also more likely to experience difficulty obtaining and using contraception, have multiple sexual partners, and have more unintended pregnancies, and are at high risk for physical and sexual assault.^21,27 Homeless children also have poor health. They suffer from more infectious diseases such as respiratory tract infections and diarrhea and have more nutritional disorders, asthma, and developmental delay than children with homes.²⁶

Homeless individuals have high rates of smoking; approximately three-fourths of homeless adults are smokers.²⁸ While smoking rates have decreased in the general population, rates have not decreased in homeless populations. Smoking-related illnesses, including chronic obstructive pulmonary disease and cancer, are major threats to the health of homeless individuals.

Homeless individuals age 50 and older have rates of geriatric conditions, such as cognitive and functional impairment, similar to those over 20 years and older.²⁹ While health-care providers focusing on homeless adults have focused, traditionally, on acute and communicable diseases, the aging of the homeless population has increased the need to manage multiple chronic medical conditions, such as diabetes, hypertension, coronary artery disease, and chronic obstructive pulmonary disease which are often undiagnosed or inadequately treated in this population.

Rates of mental illness have varied widely among the homeless but are consistently higher than the general population. A nationally representative study of homeless individuals found that 57% of currently homeless individuals had a mental health problem in their lifetime and 39% currently suffer with a mental illness.²² The relative prevalence of different types of psychiatric impairments mirrors that in the general population, with depression, bipolar affective disorder, schizophrenia, posttraumatic stress disorder, and personality disorders being the most common.³⁰ Severe mental illness is more common among the chronically homeless population than other homeless populations, although rates are elevated throughout the homeless population.

In addition, homeless people have a high rate of substance use, which can complicate the medical care that they receive. Thirty-eight percent of currently homeless clients in a national survey were found to have a current alcohol problem, and 62% had an alcohol problem in their lifetime.²² Approximately 25% of currently homeless persons have a problem with drug use, and 60% have a lifetime history of a drug use disorder.²² Sixty-six percent of currently homeless persons have at least one mental health, alcohol, or drug problem; 86% have had at least one of the three problems in their lifetimes. Many have at least two of the three problems simultaneously. Thirty percent of homeless clients have a lifetime history of mental health and alcohol and drug problems.²²

Homeless people have higher rates of inpatient hospitalizations than housed persons, likely because of delayed access to care and lower admission thresholds. Complying with both outpatient and discharge treatment plans may be more difficult, particularly if providers do not consider housing status when developing treatment plans.