Social Rejection, Isolation, and Substance Use Disorders: A Neurobiological Defense of Social Network Intervention in Single-Site Housing First

Abstract Introduction: Rising rates of homelessness in the United States demand not only increased housing efforts but also comprehensive strategies addressing the underlying causes of chronic homelessness. Among the most prevalent factors is substance use disorder (SUD), which both contributes to and results from housing instability. Conventional abstinence-based treatment models often fail to address the root causes of substance use, particularly the chronic social isolation and rejection experienced by the unhoused. This thesis argues for the adoption of a neuroscience-informed model of recovery rooted in community reintegration and low-barrier housing with on-site support services. The Neuroscience of Substance Use Disorders and Social Stress: Substance use disorders are deeply intertwined with neurobiological changes caused by chronic stress, especially social rejection and isolation. These adverse social experiences dysregulate key brain regions—such as the amygdala, hippocampus, prefrontal cortex (PFC), and the hypothalamic-pituitary-adrenal (HPA) axis—leading to heightened stress responses, impaired executive function, and increased sensitivity to drug-related cues. The resulting negative affect and compromised decision-making capabilities create a cycle of stress-induced drug seeking. Rodent studies further support these findings, showing that social defeat and isolation significantly increase drug self-administration and relapse-like behavior as modeled by conditioned place preference. A Social Housing Model for Substance Use Disorder Treatment: Single-Site Housing First (SSHF) programs offer an alternative to traditional abstinence-based models by providing immediate, low-barrier, permanent housing combined with voluntary support services. SSHF prioritizes safety, autonomy, and the cultivation of positive social interactions, creating an environment conducive to both behavioral and biological healing. Residents report enhanced feelings of safety, self-worth, and motivation for recovery, as well as reduced substance use. Incorporating interventions such as Motivational Interviewing Social Network Intervention (MI-SNI) can further enhance social reintegration and reduce substance use by helping residents identify and strengthen supportive relationships. Discussion: SSHF not only facilitates housing stability but also addresses the neurobiological effects of social stress that perpetuate substance use. The model allows for a self-directed approach to recovery, enabling residents to re-engage with community resources and build supportive networks. While current research on SSHF and substance use outcomes is limited, especially for long term SUD outcomes, preliminary findings indicate improvements in social integration, reduced relapse risk, and enhanced housing stability. These benefits highlight the necessity of social connection in overcoming addiction and suggest that promoting high-quality social networks should be a core component of SUD treatment. Conclusions: The intersection of neuroscience, housing policy, and social support intervention offers a compelling framework for addressing substance use in unhoused populations. SSHF, especially when combined with social network interventions, represents a promising evidence-based approach to breaking the cycle of chronic homelessness and SUD. By reconceptualizing substance use as a maladaptive response to social stress, we can develop more effective, client-centered treatment plans.