Homeless youth face unique challenges ensuing from a broad array of unmet health needs. In this article, we explore the health risks faced by this population, focusing on substance abuse and mental illness, and behavioral risk factors relating to hepatitis C virus (HCV) and other blood-borne infections. In addition, we discuss approaches for addressing medical and psychological factors associated with substance use and mental illness through behavioral interventions and interdisciplinary, youth-centered care. Such targeted strategies are critical if we are to be effective in our efforts at prevention and risk reduction in vulnerable populations, such as homeless youth, and addressing the ‘silent epidemic’ of hepatitis C in the United States and abroad.
Homeless youth in the United States
Nationwide, there are an estimated 1–2 million homeless youth in the United States, including ‘throw-away’ (those who have been thrown out of their homes by family members) and ‘runaway’ (those who voluntarily leave their homes) youth, as well as a small number who live within homeless families [1,2].
A national study of homeless youths  found that 68% are 15–17 years old; 57% are Caucasian, 17% are African American, 15% are Hispanic and 12% are of other ethnic origins, with males and females equally represented. In urban centers such as Los Angeles, the homeless population is often overrepresented by youth. According to the US Census Bureau  and Bring LA Home , 62% of the homeless population in Los Angeles is under the age of 30 years. In contrast to national figures, homeless female youth in Los Angeles outnumber men, particularly among those aged 18–29 years, many of whom are single mothers with young children or babies. Given the lack of shelter beds and temperate weather, a majority of unaccompanied youth in Los Angeles end up on the street for varying amounts of time, and once there, may be easily integrated into the street economy with its ensuing health risks [6,7].
Youth become homeless for a variety of reasons ; the most common precipitating factor is family conflict or dysfunction. In a study of homeless adolescents in San Francisco, Denver, and New York City, 59% cited family conflict and 22% cited abuse or rape by a family member as the precipitating factor . In addition, over a quarter of all homeless youth in the USA have been institutionalized or under foster care before becoming homeless. This group has been shown to be at a particularly high risk of drug use, sexual risk behaviors, depression and poverty . In Los Angeles, 45% of the approximately 1000 foster youth that emancipate each year from the foster care system will be released directly onto the streets or will end up there within 6 months .
Sheltered versus street youth
Although accurate census data on the number of ‘sheltered’ versus street youth are unavailable as a result of sampling limitations and the relative mobility of homeless youth, point-prevalence studies have revealed that over 50% of youth are identified as primarily street based and engage in riskier behaviors, and report poorer health status, higher daily stress and fewer health-seeking behaviors than their counterparts living in shelters or within homeless families [12,13].
Homeless youth residing in shelters face the challenges of crowded conditions, limited privacy, loss of autonomy, and strict rules. Many youth find shelter rules, which dictate when one may enter, depart, sleep, bathe, and eat, to be stifling. Such barriers to privacy and self-determination may lead youth to reject life in a homeless shelter  in favor of the relative freedom of the streets.
Although street life may present an appealing alternative to the limitations of homeless shelters, the constant struggle to find a safe, secure environment, generate income, and obtain sufficient food adds instability and chaos to an already disrupted life . Living on the street confers a high risk of violence and victimization, and increases the likelihood of adverse survival behaviors such as prostitution and petty crime. In their study of 272 homeless street youth, Wagner et al.  reported that 35% were beaten, 39% were robbed, and 44% were threatened with a gun. Forty-seven per cent of females and 35% of males were propositioned to sell sex, and 31% of females and 13% of males were sexually assaulted. Often, the adaptive response to chronic stress, danger and isolation is immersion into the street culture. Such adaptation may result in a gradual estrangement from society and the ‘safety net’ services it provides .
As a result, it is important that care for this population be youth-centered and culturally sensitive. The concept of ‘one-stop shopping’ with services provided at sites frequented by street, as well as sheltered or accompanied youth, may enhance access and care and facilitate a multidisciplinary approach to the complex and diverse mental, social and physical health needs of this vulnerable population.
Large-scale, national studies have found that 70–97% of homeless youth abuse alcohol, drugs or both [9,10], with the risk increasing with age and the duration of homelessness . These studies of homeless youth aged 12–21 years revealed that for nearly every drug surveyed, youths residing on the street had significantly higher rates of drug abuse than their age and socioeconomically matched peers living at home or residing in shelters: approximately 75% of street youths reported using marijuana; one-third used hallucinogens, stimulants and analgesics, and nearly 25% used crack, other forms of cocaine, inhalants, and sedatives. In contrast, 43% of sheltered youth reported using marijuana, 13% used hallucinogens, stimulants, and analgesics, 7% used crack and other forms of cocaine, and 2% engaged in injection drug use .
Street youth are also more likely to engage in higher risk substance use than their sheltered peers. Among street youth in Los Angeles, 30% reported using injection drugs, and of these, 59% had shared needles . Heroin is the most commonly injected drug, followed by cocaine and speedball.
Mental illness is prevalent among homeless youth compared with housed youth, with a threefold higher rate of Diagnostic and Statistical Manual of Mental Disorders version IV disorders than in the general youth population . Among homeless and runaway youth, Peterson and colleagues  reported that 35% exceeded the clinical cut-off scores on measures of depressive symptoms. Factors commonly associated with depressive symptomatology in homeless youth include a history of physical or sexual abuse, a greater number of negative life events and lower levels of social support available to deal with life crises. Mood disorders, anxiety, hypervigilence, and symptoms of attention deficit hyperactivity disorder are especially prevalent among homeless youths who use alcohol and other drugs [7,8]. In a nationwide survey of 1240 homeless youths, Green and associates  found that a quarter to a third had attempted suicide at least once, with nearly half citing the use of alcohol or drugs as a causative factor . Several researchers have suggested that the high correlation between mental illness and substance abuse disorders may suggest an attempt by those with mental health problems to self-medicate .
In addition to a high prevalence of Diagnostic and Statistical Manual of Mental Disorders version IV diagnoses, poor parental modeling, previous abuse and low self esteem may compromise the development of adequate coping skills and leave youths particularly vulnerable to the daily stressors associated with life on the street . Inappropriate or dysfunctional social support, complicated by mental health issues including depression and attention deficit hyperactivity disorder, may present significant barriers to securing the necessities of daily living, and may interfere with health-seeking and other positive adaptive behaviors [7,8].
Risky sexual activity and sequelae
The majority of homeless youths are sexually active by the age of 16 years. Kral and associates  found that 98% of youths aged 12–19 years are sexually active, with nearly half engaging in sexual intercourse by the age of 13 years. Unwanted pregnancy is common, with nearly 50% of homeless females reporting a previous or current pregnancy . Homeless youths frequently engage in risky sexual practices including unprotected sex with multiple partners, ‘survival sex’ in exchange for food, drugs or money, male-to-male sexual activity, sex while under the influence of drugs or alcohol, and other behaviors that expose them to hepatitis, HIV, and other sexually transmitted infections . Those using heroin, methamphetamine, or cocaine exhibit more sexual risk taking than non-users .
Hepatitis B virus infection
Homeless and runaway youths are vulnerable to hepatitis B virus (HBV) infection , as a result of high-risk behaviors and a frequent lack of previous vaccination. National samples of homeless youth suggest a high HBV prevalence, with a Los Angeles-based study of injection drug user youth revealing an HBV prevalence of 18.5% , and a study in South Carolina  reporting that 22% of homeless youths tested were positive for HBV, HCV or both. Unprotected sex is the predominant risk factor for HBV in youths , with injection drug use, intranasal cocaine, and poor dental hygiene representing additional routes for HBV infection [23,24]. Whereas Centers for Disease Control and Prevention guidelines mandate universal vaccination for individuals under the age of 18 years and for all adults who engage in risky sexual practices, have pre-existing liver disease or use injection drugs; homeless youths are often missed by school-based vaccination programmes, and there is evidence to suggest that nearly 50% of the current youth population has not been fully vaccinated against HBV .
Given that chronic HBV is a vaccine-preventable disease, and concurrent infection with HCV, HBV or acute hepatitis A virus (HAV) [23,25] has been shown to worsen the risk of disease morbidity, the institution of HAV/HBV immunization programmes targeted at homeless youth is a compelling priority. Based on the observation in adults that HBV vaccination enhances the immune clearance of HCV , there may exist an added therapeutic benefit in immunizing those with HCV.
Hepatitis C virus infection
HCV infection is the most common bloodborne infection nationwide, with an estimated 3.9 million infected and 2.7 million having chronic disease . Homeless youths, particularly those with injection drug or cocaine use, previous incarceration, tattooing, risky sexual practices, mental illness, and the sharing of personal items , prostitution or victimization, and possibly severe peridontal disease are at a significant risk of HCV [20,29,30].
Whereas statistics regarding HCV prevalence in homeless youths are limited, national estimates range from 4 to 38% [19,31–33] depending on the time homeless, age and cumulative risk factors. Los Angeles-based findings in the ongoing Drug Users Intervention Trial, a study funded by the Centers for Disease Control and Prevention aimed at preventing new HIV and HCV infections among 15–30-year-old drug users, revealed baseline HCV prevalence rates of 0% in injection drug users aged 15–17 years, 16.3% in those aged 18–21 years, 30.6% in those aged 22–25 years, and 34.7% in those aged 26–30 years . The results correlate with previously published rates of 20–45% among homeless adults in Los Angeles , and suggest a potential window of opportunity for risk reduction in homeless youth. However, as a result of the lack of health-seeking behavior or the availability of preventative health services, few homeless youth are aware of their risks , and the majority of those at high risk of HCV have never been tested . Furthermore, once infected, homeless youths may be less likely than adults to seek medical care and other health services .
Co-infection with HIV and hepatitis C virus
Of the nearly 800 000 HCV-infected individuals in the USA, approximately 16–25% are co-infected with HIV . As a result of shared risk factors, HIV/HCV co-infection is common among the homeless and urban poor, with approximately 70% of HIV-positive individuals demonstrating concurrent HCV infection . The majority of co-infected individuals have reportedly engaged in injection drug use behaviors and the sharing of drug paraphernalia . Co-infection is associated with higher rates of viral replication , and a poorer prognosis for both HCV  and HIV than with either disease alone . With HCV listed as the third leading cause of death  in HIV-infected individuals, strategies aimed at reducing the risk of blood-borne pathogen transmission among homeless youth are critical, and given the disease burden related to HCV and HIV as a function of age, are likely to prove cost effective.
Integrated strategies for homeless youth
As a result of the high prevalence of injection drug use, non-injection substance use, mental illness, risky sexual practices, the limited use of preventative health services, including vaccination programmes, a lack of knowledge about hepatitis and HIV, and a lack of information on risk reduction behaviors [21,28], homeless youths are at a great risk of hepatitis, HIV and other blood-borne communicable diseases . There is an acute need for youth-centered programmes that integrate primary health services, dental care, risk reduction, mental health services and substance abuse treatment in the outpatient ‘one-stop shopping’ setting.
As homeless youths are more likely to access drop-in centers and shelters than medical clinics , it has been proposed that treatment programmes be based at these sites and incorporate ‘youth-savvy’ outreach to those living on the streets. The concurrent provision of mental health services, including the treatment of depression and substance abuse, may improve compliance and long-term outcomes . In a recent study by Asarnow et al.  it was found that clinical interventions for depression in youth were more effective in the primary care setting compared with referral to a specialist, reinforcing the benefit of the direct integration of mental health services at primary care sites . Barriers to an integrated approach include a lack of funding and the long-standing separation between substance abuse treatment, medical care and psychiatric services . These issues must be considered and balanced with the traditional barriers to care faced by homeless youth, including concerns regarding confidentiality, the cost of services, lack of insurance, lack of transportation, cultural, spiritual and language barriers, discrimination, fear of receiving a bad diagnosis, distrust of healthcare providers, not knowing where to go, feeling embarrassed to ask for healthcare, and distrust of social workers and police . It is known that adolescents with substance abuse and comorbid psychiatric disorders have poorer drug treatment outcomes than youths with only substance abuse disorders; thus, early screening for co-existing conditions is critical . Staff who work with homeless youths should be well versed in state-specific mandatory reporting laws and other state or national legislation that may impact youth and their health providers. In addition, staff should receive specific training in the administration of screening instruments that have been rigorously evaluated for reliability and validity  among homeless populations.
The identification of potential substance use disorders can be as brief as asking four questions that probe for problem alcohol use and then querying 30-day use of a list of illicit drugs. The Rapid Alcohol Problems Screen-4 (RAPS4) , featured in Table 1, is brief and has better specificity and sensitivity for screening alcohol abuse or dependence disorders with fewer sex and ethnicity biases than the more familiar CAGE questions (Cutting down on drinking, Annoyed by criticism, Guilty about drinking, Eye-opener in the morning). The identification of potential drug use disorders can be efficiently conducted by capturing the 30-day use of various illicit drugs (marijuana, opiates, benzodiazepines, other sedatives/hypnotics, cocaine, amphetamines, hallucinogens, inhalants, club drugs, multiple drugs at one time) using the drug reporting section of the Addiction Severity Index . Riggs et al.  have outlined the following steps for successful treatment design and delivery: (i) convene a comprehensive case conference with experts who represent substance abuse, mental health, physical health, family therapists (if appropriate) and community agency representation; (ii) use a collaborative approach to stabilize substance use and treat the comorbid disorders; (iii) carefully consider pharmacological therapy; (iv) re-evaluate and reassess progress or change approaches; and (v) discuss relapse prevention strategies with the youth. Such innovative approaches, which promote treatment integration for at-risk youth and incorporate behavioral interventional techniques such as strengths-based case management (SBCM) and motivational interviewing, are expected to overcome many of the traditional systemic and personal barriers faced by this homeless population.
Strengths-based case management
Case management has been shown to be an effective strategy for decreasing the need for emergency services, enhancing quality of life and self-efficacy, and ensuring a smooth transition of individuals moving through a fragmented healthcare system . SBCM is defined as an approach whereby youths are assigned case managers who determine the strengths of the youths while enhancing effective coping skills, communication, self-esteem, and knowledge about hepatitis and HIV. In addition, SBCM allows advocacy and the facilitation of services through efforts such as scheduling and personally escorting youths to service agencies or assisting in follow-up. SBCM programmes can focus on the avoidance of health-risk behaviors, increasing access to medical care, referrals to health services such as drug treatment programmes and social services, or on supporting compliance with an intervention, such as a 6-month HAV/HBV vaccination series. In its study of homeless injection drug using youth, the AIDS Evaluation of Street Outreach Project (AESOP) in San Francisco demonstrated that higher levels of contact and interaction with outreach workers resulted in a greater number of referrals, improved follow-through on HIV-related referrals, and a lower likelihood of high-risk injection drug use behaviors, such as reusing needles for injection .
Utilizing an SBCM approach, injection drug use, unprotected sex, and poor hygiene as risk factors in varying degrees for hepatitis and HIV can be addressed, along with the risks of sharing needles and drug preparation items, such as cookers, cotton or rinse water, and the potential hazards of tattooing and body piercing, sharing toothbrushes and razors, and co-infection of hepatitis and HIV. In addition, the impact of hepatitis or HIV on affected individuals, and the importance of positive social relationships can be addressed. Positive coping skills (positive action, social support, and spiritual hope) along with techniques for stress reduction and self-care behaviors should be reinforced . Finally, a model for problem-solving in difficult situations can be presented. Through the process of setting goals, generating and evaluating alternative methods for achieving these goals, and examining the projected outcomes and consequences of each action, facilitators may promote active problem-solving and self-efficacy among participants. Strengths-based approaches, such as SBCM and motivational interviewing described below, are complementary when intervening with homeless youth; both hinging on facilitators who are respectful, culturally competent, and able to present the pros and cons of specific actions on health-related behaviors in a non-judgmental way. Through this process, youth may gradually ‘re-programme’ non-adaptive behaviors or responses learned through poor parental modeling and other adverse circumstances.
Motivational interviewing as a therapeutic adjunct to care
Motivational interviewing is a brief psychotherapeutic intervention designed to facilitate and enhance one's intrinsic motivation to change behavior . Brief motivational interviewing has been found to be an effective strategy with youth as it is non-confrontational, and free from prescribed outcomes , allowing facilitators to meet youth ‘where they are at’. Group-facilitated motivational interviewing sessions can be provided in primary care settings weekly, in conjunction with efforts such as HBV/HAV immunization programmes. The successful use of group-focused motivational interviewing has been demonstrated in youths aged 16–21 years in reducing drug use and improving the perception of drug-related risk and harm .
There are two motivational interviewing models that offer parallel strategies for delivering health-related interventions, one of which (BRENDA) has been successfully applied to youth with substance use and risk behaviors . The BRENDA strategy is represented by an acronym that details six primary aspects of the counseling approach: Biopsychosocial evaluation, Reporting, Empathy, Needs assessment, Direct advice, and Assessment of treatment progress. After screening, an adolescent-specific interview generally takes the approach of Riggs et al.  and follows standard practice guidelines for treating adolescents with substance use and potential concomitant mental disorders . In the case of homeless youth, motivational interviewing sessions can focus on the progressive coverage of practical issues such as survival on the street, alcohol and drugs, emotions and what to do with them, and connecting with communities, while respecting the importance of personal agency and integrating youth subculture.
An additional benefit to multidisciplinary strategies that utilize motivational interviewing and SBCM is the opportunity for continuity, and, over time, a more intimate and comprehensive assessment than would otherwise be possible with fragmented, episodic healthcare. In this way, comorbid conditions such as substance use and psychiatric disorders may be diagnosed earlier and integrated into the therapeutic approach, thereby mitigating treatment failures that may result when such disorders are treated in isolation .
Homeless youth are a high-risk and vulnerable population that is often missed by conventional healthcare services because of numerous cultural, personal, and economic factors. It is crucial that healthcare workers become aware of the unique challenges and risks faced by this population. Although there is general consensus on the healthcare needs of homeless youth, including targeted immunization programmes, risk reduction and preventative health services, the means to achieve these goals and address issues of access and compliance have been elusive. Integrated mental health, substance abuse and medical services at drop-in centers and other community sites where homeless youth congregate may be effective in improving service utilization and long-term outcomes. Culturally competent care that addresses the needs of homeless youth for self-determination and autonomy, while providing a structure of peer and individual support through techniques such as motivational interviewing and targeted case management, may facilitate engagement and compliance with behavioral change in this high-risk group. Additional research and intervention studies are needed to refine our understanding of how best to deliver cost-effective, quality care for homeless youth and guide public policy. Ultimately, providing stable, affordable housing, intervening with high-risk youth or families before they become homeless, and addressing the root causes of homelessness among youth, particularly that of childhood abuse, must play a pivotal role in our global efforts.
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