Opioid overdose has become an increasingly salient public health crisis in the United States in recent years. According to Centers for Disease Control, U.S. overdose deaths increased by 28.5% from Spring of 2021 to Spring of 2022 (1). For people who inject drugs (PWID), the overdose crisis is compounded by the co-occurring affordable housing crisis in the U.S., particularly in major cities, where stable housing has become increasingly difficult to obtain. Between 2021 and 2022 home rental and apartment rental pricing increased by over 10% and 20%, respectively in major metropolitan areas (2), which has fostered an increase in homeless populations with the latest data showing a 2% increase in homelessness from 2019 to 2020 (3).
A growing body of research has highlighted the importance of addressing structural factors, including housing, that contribute to substance misuse and its adverse outcomes such as overdose (4–10). PWID are particularly susceptible to recurrent housing instability (i.e., lack of access to stable housing) due to ongoing barriers to maintaining and accessing housing (11, 12). As a result, PWID who begin to experience housing instability often remain in a state of long-term, cyclical homelessness (12). Theoretically, housing instability can increase stress, depression, and anxiety, all of which are associated with increased risk for overdose (13–21). Housing instability is also directly associated with increased risk of overdose in some (5, 9, 14, 22–27), but not all studies (28–30), perhaps partly due to the inconsistent conceptualizations of housing instability across studies. Mechanisms that might explain this relationship include more intense or risky patterns of substance misuse among homeless PWID (31–33), and rushed injection in public spaces (34–36). Recent incarceration entailing loss of tolerance may also play a role (37, 38).
Most prior overdose-focused research studies have measured housing stability using three main constructs—unstable residence, homelessness, and residential mobility/transience—operationalized in varying ways. Multiple studies have used a dichotomous measure that identifies housing as stable or unstable using the type of housing (e.g., home, shelter) that individuals have recently resided in to make this determination as the indicator (4–6). Alternatively, a dichotomized measure of homelessness has been used by researchers, but this categorization is inconsistently determined by either self-report or using individuals’ recent housing type (22, 24, 26, 27). Studies have also examined housing status using the construct of residential mobility/transience, which is typically measured using the number of residences or communities lived in during a period of time (8, 9, 14, 28, 39).
Research examining the relationship between housing and opioid overdose typically has focused on a single component of housing instability, the most common of which are housing type, housing tenure, or self-reported homelessness. Housing type is typically based on the type of residence (e.g., house/apartment, hotel/motel, abandoned building, shelter, etc.) (4, 5, 23, 24, 26, 29, 30); housing tenure dichotomizes stable and unstable housing or residential mobility/transience based on the length of time an individual has lived in a location or alternatively based on the number of moves an individual has undergone in a defined time period (14, 16, 19, 39); and homelessness relies on self-reported homelessness or determinations based on housing type to identify individuals as homeless (22, 24, 25). Used alone, each operationalization is limited in capturing housing instability. For example, for housing type, what constitutes stable residence varies in the literature and often does not account for length of residency at each type (8, 9, 14, 28, 39–41). Moreover, housing tenure does not capture the quality of the residence, and therefore, may incorrectly identify long-term stays in unsafe environments as stable housing (42). Finally, self-reported homelessness is often defined by varying lengths of time and severity (e.g., live in a shelter or street) or unclearly defined, which could lead to biased responses due to varying definitions of homelessness (41).
To address the limitations of single-factor measures of housing instability, Frederick et al. proposed that housing instability measures should be multi-dimensional, an argument that is supported by other housing researchers attempting to improve measures of housing instability (41, 43, 44). Specifically, Frederick et al. suggested a measure that includes assessments of housing type, tenure, legal status (criminal justice involvement), employment, and income (41). Frederick et al. argued for the inclusion of items that affect stability such as employment and legal status to measure risk of housing instability over time, rather than a static condition of housing (41). Dynamic measures of housing instability such as this have been called for to address the inherently fluid nature of housing status (45, 46).
To some extent, researchers have heeded the call for more multi-dimensional measures of housing stability by combining constructs or increasing the number of categories within constructs in an effort to create more robust measures of housing instability. Examples include (i) Whittaker et al. (2015), who used housing type to dichotomously categorize individuals as homeless or stably housed; (ii) Calvo et al. (2017) who combined homelessness and stable housing using a three-category measure; and (iii) Perez-Figueroa et al. (2021), who created a four-category (unhoused, imminent risk of homelessness, precarious housing, and stable housing) measure of housing stability based on housing type. These studies go beyond the commonly used dichotomous measures of housing instability; however, they do not go so far as to account for factors that can impact housing instability risk such as employment, income, and criminal justice involvement as called for by housing researchers, and they still only address one dimension of housing instability (41, 43, 44). Therefore, there is a need to unify these constructs under a single index measure of housing instability risk in order to better understand the role of “housing status” more holistically as a potential predictor of overdose and other substance use-related outcomes.
Our study will bridge the gap between opioid overdose and housing literature by examining the relationship between a multi-dimensional measure of housing instability and lifetime overdose count among a cohort of young PWID in the Chicago Metropolitan Area, which includes the city of Chicago (Cook County) and the surrounding suburbs in Cook County and its adjacent counties that are also the five most populous counties after Cook County (DuPage, Kane, Lake, McHenry, and Will Counties). To holistically encapsulate housing instability risk, the measure will consider housing tenure, housing type, and self-reported homelessness as well as employment, income, and criminal justice involvement (i.e., prior incarcerations). Unifying these factors into a single measure of housing instability risk is proposed to reduce inconsistency in the constructs used to capture housing instability when examining its relationship with overdose.