How substance use and psychosis affect mortality among homeless adults in Vancouver | Research

The takeaway

Among 437 homeless or precariously housed adults in Vancouver, both substance use disorders and psychotic disorders were associated with increased mortality over a 10-year follow-up.

Public health researchers, clinicians working with homeless populations, and policy makers.

437 homeless adults followed for 10 years

What the researchers found

Over 10 years of follow-up, participants with co-occurring substance use and psychotic disorders had higher mortality rates than those with either condition alone. Cannabis use was one of several substances assessed, though injection drug use carried the highest mortality risk.

Why it matters

Homelessness, substance use, and mental illness often co-occur, but few studies track mortality outcomes over extended periods in this population. The findings highlight the compounding risks when multiple conditions overlap.

The numbers in context

437 participants; 10-year follow-up period; mortality data linked through provincial vital statistics.

How the study worked

Prospective longitudinal cohort study following 437 homeless or precariously housed adults in Vancouver for up to 10 years, with structured diagnostic interviews at baseline.

What this study cannot tell us

Single city (Vancouver); cannabis use was one of many substances examined and not isolated as an independent risk factor; attrition challenges inherent to studying homeless populations.

How to read the evidence

Moderate: longitudinal design with diagnostic interviews, but single-city sample and cannabis not isolated from other substances.

When this study was published

Published 2016.

The bigger picture

This study underscores that addressing substance use or mental illness alone may not be sufficient. The intersection of homelessness, psychosis, and substance use creates compounding vulnerability that requires integrated approaches.

Questions still open

What specific interventions could reduce mortality in this high-risk population? How does the legalization of cannabis in Canada affect substance use patterns among homeless individuals?

Common questions

Did cannabis use specifically increase mortality risk?

The study assessed multiple substances together. Cannabis use was part of the broader substance use assessment, but injection drug use, not cannabis specifically, carried the highest mortality risk.

What increased mortality risk most?

The combination of psychotic disorders and substance use disorders together was associated with higher mortality than either condition alone.

Read the original research

Associations of substance use, psychosis, and mortality among people living in precarious housing or homelessness: A longitudinal, community-based study in Vancouver, Canada.

PLoS medicine, 17(7), e1003172

View on PubMed ↗Publisher’s paper ↗

Citation

Jones, Andrea A; Gicas, Kristina M; Seyedin, Sam; Willi, Taylor S; Leonova, Olga; Vila-Rodriguez, Fidel; Procyshyn, Ric M; Smith, Geoffrey N; Schmitt, Toby A; Vertinsky, A Talia; Buchanan, Tari; Rauscher, Alex; Lang, Donna J; MacEwan, G William; Lima, Viviane D; Montaner, Julio S G; Panenka, William J; Barr, Alasdair M; Thornton, Allen E; Honer, William G. (2020). Associations of substance use, psychosis, and mortality among people living in precarious housing or homelessness: A longitudinal, community-based study in Vancouver, Canada.. PLoS medicine, 17(7), e1003172. https://doi.org/10.1371/journal.pmed.1003172