Cannabis Use as a Moderator of the Association Between Insight and Depression in Early Psychosis: Results From a Prospective Study

Abstract

Background: A high level of insight in first episode psychosis (FEP) is positively correlated to important prognostic factors such as medication adherence and functional outcome but is associated with increased depression level and suicidal behavior. This is the first study questioning the potential moderating role of cannabis use in the relationship between insight and depression one year after a FEP. Methods: In this prospective observational study, we enrolled 214 FEP patients who had been referred to a specialized early psychosis program and followed for 36 months. A series of multivariate regression models were used. Baseline insight, medication adherence and cannabis use (level of use on a continuum) were entered as independent variables while the PANSS positive score, PANSS negative score, the MADRS score and the GAF score after one year were alternately selected as the dependent variable. Outcomes: We found a three-way interaction term between cannabis use, insight and medication adherence on depression level one year after the entry into the program. A high level of insight was significantly associated with higher MADRS scores in patients with high cannabis use, while depression decreased in high-insight patients with low cannabis use. Interpretation: Cannabis use continuation during the year following a first episode psychosis may play a significant role in the development or the maintenance of post-psychotic depression in patients who present with high level of insight and adherence to medication, stressing the need for specific therapeutic strategies in this subgroup of patients. Funding Statement: The authors declare: No funding. Declaration of Interests: The authors have no conflicts of interest to disclose and have not been paid for this article. Ethics Approval Statement: The Research and Ethics Committee of the Faculty of Biology and Medicine of Lausanne University granted permission to access all clinical data for research purposes, and all patients who enter the program do so on a voluntary basis and are automatically included in the study if they meet the clinical inclusion criteria.