Heroin Use, Traumatic Brain Injury, and Schizophrenia Predict Everyday and Social Functioning in Marginally Housed Persons: Direct Effects and Mediation by Neurocognition

Multimorbid illness, including substance use, psychiatric illness, viral infection, and traumatic brain injury (TBI), is prevalent in marginally housed persons, but it is unclear how these problems influence everyday and social functioning. We conducted mediation analyses in 210 participants in order to evaluate the effects of substance use, psychiatric illness, viral infection, and traumatic brain injury on predicting 6-month follow-up ratings of functioning, and to examine whether neurocognitive performance significantly mediated the relationship between these health characteristics and ratings of functioning. Neurocognition, alongside positive and negative symptoms, explained 47% of the effect of schizophrenia on functioning and 11% of the effect of TBI on functioning. Additionally, greater heroin use frequency was significantly associated with lower ratings of functioning, but this effect was not mediated by neurocognition. Our findings highlight the role of neurocognition in mediating the relationship between illness and functioning in the marginally housed, and inform treatment targeting toward specific morbidities in populations with complex health issues.