An estimated 750,000 to 2 million Americans age 18 to 24 years experience homelessness in any given year (Ammerman et al., 2004). The prevalence of substance use disorders among these young adults is 3 to 4 times higher than that of their never-homeless counterparts (Reardon et al., 2003; Shelton et al., 2009), with about half having a history of alcohol disorders and approximately one third having a history of drug disorders (Koegel et al., 1996). Substance use has been linked to family dissolution, social isolation, and poor job performance, all of which contribute to homelessness (van den Bree et al., 2009). A better understanding of factors that increase the risk for substance use among homeless young adults may aid in developing appropriate prevention and treatment.

Childhood maltreatment, including childhood sexual abuse (Briere, 1988) and other adverse experiences (Felitti et al., 1998), increases risk for later substance use (Kendler et al., 2000; Nelson et al., 2006). Child maltreatment is a common reason for removing children from their homes and placing them in foster care (Garland et al., 1996). Other determinants of foster care placement include parental problems, such as substance abuse and incarceration. Most children and adolescents in foster care are removed from their homes for these reasons (Fowler et al., 2009; Zlotnick, 2009).

Foster care placement is associated with many traumatic experiences in its own right, including residential and educational instability (McMillen et al., 2003; Courtney and Dworsky, 2004) and decreased social, emotional, and financial support (Courtney and Dworsky, 2005), all associated with increased risk for homelessness and substance use (Caton et al., 2005; Shelton et al., 2009).

A history of foster care is reported by a high proportion of homeless young adults (Park et al., 2005; Fowler et al., 2009). Substance use among young adults who exited foster care has been consistently reported at rates higher than those in the general population (Simms et al., 2000; Thompson and Auslander, 2007; Vaughn et al., 2007). However, the association between a history of foster care and substance use among homeless young adults has received surprisingly little attention. Given the potential salience of substance use to poor outcomes of both foster care and homelessness, knowing whether a history of foster care adds to our understanding of substance use among homeless young adults is of high importance.

Specifically, no information is available on whether, after controlling for the influences of demographics and other potential risk factors, a history of foster care is associated with substance use among homeless young adults. To that end, the present study examined the substance use of homeless young adults seeking crisis shelter with and without histories of foster care placements. The purpose of the study was to examine the following hypotheses: (1) a history of foster care would be associated with substance use; and (2) foster care would remain related to substance use, controlling for demographics and other known risk factors, including childhood maltreatment, arrest, unemployment, lack of high school diploma, and family drug use.