Cognitive performance and lifetime cannabis use in patients with first-episode schizophrenia spectrum disorder

ABSTRACT

Introduction

Cognitive impairment is among the core features of schizophrenia. In a healthy population, the cognitive deficit is often linked with cannabis abuse, and although the same would be expected in patients with schizophrenia, research has presented contradictory results.

Methods

Participants were patients with first-episode schizophrenia (FES) spectrum disorder who had been lifetime cannabis users (N = 30), FES non-users (N = 53) as well as healthy controls (HC) also divided into cannabis users (N = 20) and non-users (N = 49). All participants underwent an extensive neurocognitive assessment and filled in a cannabis questionnaire, which allowed for a comparison of the four groups on cognitive functioning.

Results

FES patients using cannabis showed less impaired cognitive functioning with the most prominent difference in visual memory compared to FES non-users. However, they differed neither in the clinical assessment of general psychopathology, positive and negative symptoms, nor in medication from the patient’s non-users. A comparison of the HC who used cannabis, and those who did not, revealed no sizeable differences in cognitive performance between the groups.

Conclusions

The results delivered supporting evidence for the trend of superior neurocognitive performance in FES patients with a lifetime history of cannabis use compared to non-using patients.

KEYWORDS:

• Schizophrenia
• cognition
• cannabis
• substance use
• psychosis

Disclosure statement

The authors report no conflict of interest.

Data availability statement

The data that support the findings of this study are available from the corresponding author, K. Knížková, upon reasonable request.

Additional information

Funding

This publication was supported by the project No. LO1611 with financial support from the Ministry of Education, Youth and Sports of the Czech Republic (MEYS) under the NPU I. programme.

Notes on contributors

M. Hájková

M. Rodriguez supervised the project and together with M. Hájková designed the study and cannabis questionnaire. K. Knížková and M. Hájková wrote the manuscript with support from M. Rodriguez and B. Keřková, A. Siroňová analysed the data and contributed to the interpretation of the results. J. Jonáš, A. Dorazilová, P. Šustová, B. Keřková, M. Hájková and K. Knížková were involved in the data collection. All of the authors discussed the results and commented on the manuscript.