A 5-year translational research program, funded by the BC Schizophrenia Society Foundation in partnership with Michael Smith Health Research BC, seeks to shed light on the complex relationship between substance use and psychosis.

Substance use disorders—defined as the problematic or harmful use of substances, often referred to as “addiction”—are a growing challenge in Canada, as reflected in rising rates of healthcare visits, hospitalizations, and overdose deaths.

Psychosis, which involves difficulty distinguishing between reality and imagination, is a core symptom of schizophrenia and related psychotic-spectrum disorders. Importantly, there is a strong overlap between substance use and psychosis: nearly half of individuals diagnosed with a psychotic disorder also meet criteria for a substance use disorder.

However, the relationship between these two conditions is complex and bidirectional. In some cases, substance use may trigger or worsen psychotic symptoms. In other cases, people living with psychosis may turn to substances for reasons that are not yet fully understood—possibly as a way to cope with distressing symptoms or medication side effects. Regardless of direction, individuals experiencing both challenges face a heightened risk of hospitalization, incarceration, and overdose.

Despite these well-known links, most research on substance use disorders has historically excluded people with psychosis; similarly, most research in schizophrenia and related psychotic illnesses exclude those with substance use disorders. In turn, this means there is very little information on best to provide care for individuals who struggle with both conditions.

Advancing Understanding and Treatment of Co-occurring Substance Use and Schizophrenia-spectrum Disorders

With his newly funded research program, Dr. Reza Rafizadeh aims to close these gaps. His team will use real-world clinical data from two major provincial centers in British Columbia to examine how medications used to treat substance use disorders and psychosis relate to overlapping outcomes, and how substance use influences treatment response and outcomes in psychosis.

The research will focus on antipsychotic medications—the primary pharmacological treatment for psychosis—and how their prescribing patterns, side effects, and effectiveness differ among patients with co-occurring substance use disorders. Dr. Rafizadeh also plans to examine how advancements in clinical pharmacology can help individualize treatment strategies to improve safety and efficacy, including the use of drug level monitoring and assessment of metabolic pathways. By illuminating these interactions, the goal is to develop clearer, evidence-based guidance to help clinicians better support individuals navigating both substance use and psychosis.

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“From a pharmacological treatment standpoint, evaluating the effectiveness of antipsychotic medications should go beyond symptom resolution to also encompass outcomes reflecting improvement in co-occurring substance use disorders, with an emphasis on enhancing autonomy and quality of life” – Dr. Rafizadeh

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