Exploring the relationship between recency and frequency of cannabis use and diminished expression and apathy as two dimensions of negative symptoms in first episode psychosis. A one-year follow-up study

Henrik Myhre Ihler,Trine Vik Lagerberg,Siv Hege Lyngstad,Ingrid Melle,Kristin Lie Romm

doi:10.1016/j.schres.2021.08.004

Henrik Myhre Ihler, Trine Vik Lagerberg + Show 3 more

Open Access

https://doi.org/10.1016/j.schres.2021.08.004

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Abstract

The association between cannabis use and negative symptoms remains unclear because of inconsistent results in existing studies. In this study we aimed to investigate the association between different aspects of cannabis use and 1) diminished expression and 2) apathy as a two-dimensional model of negative symptoms in a sample of 460 participants with first-episode psychosis. Data were collected on relevant clinical and demographic factors including diagnostics and habits of drug use at baseline, with a follow-up assessment after 12-months. We found an association between the frequency of cannabis use two years prior to baseline and the severity of diminished expression and apathy at baseline, while only the association to diminished expression held after controlling for potential clinical and demographic confounders. Frequency of cannabis use at baseline also had a significant effect on the development of diminished expression over the 12-month follow-up period. In conclusion, this study suggests that the frequency of cannabis use contributes to the severity of diminished expression at baseline, and to the progression of diminished expression after 12-months follow-up. Our findings also imply a dose-response relationship between frequency of use and severity of symptoms and add evidence to an association between cannabis use and negative symptoms.

Highlights

The association between cannabis use and negative symptoms in psychosis remains unclear
Cannabis users were significantly younger, more likely to be male, had an earlier age of onset of psychosis, more severe diminished expression, and had a higher consumption of other illicit drugs, cigarettes and alcohol compared to non-users (Table 1)
We found no significant differences between current cannabis users and non-users with respect to the mean score of the two negative symptom dimensions at 12-month follow up (p = .563 for diminished expression, p = .822 for apathy)

Summary

Introduction

The association between cannabis use and negative symptoms in psychosis remains unclear. One in four patients with schizophrenia have a comorbid cannabis use disorder (Koskinen et al, 2010), and cannabis use is associated with earlier onset of psychosis (Large et al, 2011), higher relapse rates, longer hospital admissions, and more severe posi tive symptoms (Schoeler et al, 2016). As the prevalence of cannabis use is high in schizo phrenia, and the potency of cannabis is on the rise, it is of vital impor tance to further investigate this relationship, to take appropriate measures to reduce negative symptoms

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