Adela Isvoranu

Title: Cannabis (ab)use in Psychosis: From Short- to Long-term Impact on Symptomatology


Adela Isvoranu is a PhD student at the University of Amsterdam, within the Psychological Methods research group and the Psychosystems lab group. Her PhD research is funded by an NWO Talent Grant and it is concerned with the development and application of complex system approaches to psychiatric disorders. Her work so far, which was awarded the Unilever Research Prize, has aimed to integrate (environmental and genetic) risk factors into symptom networks of psychosis and to identify pathways that may be relevant to the onset and maintenance of psychotic disorders. Her long-term aspiration is to contribute towards building a bridge between complexity science and clinical practice, with the ultimate aim of improving treatment outcomes.


Substance use disorders, especially cannabis dependence, are common comorbid diagnoses among individuals suffering from psychotic disorders. While it is generally accepted that cannabis may worsen the outcomes of psychosis, the pathways through which this effect occurs are still unclear and debated. To date, there is some evidence showing that cannabis may exacerbate positive psychotic symptoms, cognitive impairment and medication side effects (Dekker, Linszen, & de Haan, 2009), but also some evidence supporting the presence of lower negative symptom scores in cannabis-dependent patients (Salyers & Mueser, 2001).  

This talk will present results from an investigation into the effect of cannabis use on psychotic symptomatology, using novel network models (Borsboom & Cramer, 2013). We used data of patients diagnosed with a non-affective psychotic disorder from the longitudinal observational study Genetic Risk and Outcome of Psychosis Project (Korver et al., 2012). We included the second and third wave data from the Positive and Negative Syndrome Scale (PNASS), current cannabis use, and cannabis use intensity. Overall, our preliminary findings suggest that cannabis use intensity is associated with higher psychotic symptomatology in a dose-response manner and, more generally, that current cannabis use is predictive of later symptomatology.