Eye movements in patients in early psychosis with and without a history of cannabis use

Musa Basseer Sami,Ulrich Ettinger,Luciano Annibale,Philip Mcguire,Tracy Collier,Marlene Kelbrick,Savitha Eranti,Aisling O’Neill,Debasis Das,Chidimma Onyejiaka,Steve C R Williams,Sagnik Bhattacharyya,Anas Rana

doi:10.1038/s41537-021-00155-2

Abstract

It is unclear whether early psychosis in the context of cannabis use is different from psychosis without cannabis. We investigated this issue by examining whether abnormalities in oculomotor control differ between patients with psychosis with and without a history of cannabis use. We studied four groups: patients in the early phase of psychosis with a history of cannabis use (EPC; n = 28); patients in the early phase of psychosis without (EPNC; n = 25); controls with a history of cannabis use (HCC; n = 16); and controls without (HCNC; n = 22). We studied smooth pursuit eye movements using a stimulus with sinusoidal waveform at three target frequencies (0.2, 0.4 and 0.6 Hz). Participants also performed 40 antisaccade trials. There were no differences between the EPC and EPNC groups in diagnosis, symptom severity or level of functioning. We found evidence for a cannabis effect (χ2 = 23.14, p < 0.001), patient effect (χ2 = 4.84, p = 0.028) and patient × cannabis effect (χ2 = 4.20, p = 0.04) for smooth pursuit velocity gain. There was a large difference between EPC and EPNC (g = 0.76–0.86) with impairment in the non cannabis using group. We found no significant effect for antisaccade error whereas patients had fewer valid trials compared to controls. These data indicate that impairment of smooth pursuit in psychosis is more severe in patients without a history of cannabis use. This is consistent with the notion that the severity of neurobiological alterations in psychosis is lower in patients whose illness developed in the context of cannabis use.

Highlights

A history of cannabis use is arguably one of the most widely implicated modifiable risk factors in early psychosis, with a third of patients using the drug regularly at first presentation[1]
There were no significant differences between EPC and EPNC in clinical measures: time since diagnosis, age at diagnosis, current medication, days in hospital, Positive and Negative Syndrome Scale (PANSS) scores and subscales, Global Assessment of Functioning (GAF) scores and Social and General functioning
As expected, estimated fullscale IQ was lower in patients than controls, but there was no difference between EPC and EPNC

Summary

Introduction

A history of cannabis use is arguably one of the most widely implicated modifiable risk factors in early psychosis, with a third of patients using the drug regularly at first presentation[1]. Patients with early psychosis with a history of cannabis use (EPC) have a worse prognosis, unlikely to be a result of other drug use, poor adherence to treatment, genetic or environmental confounding or self-medication with cannabis in those with poor prognosis[7]. The pathway to psychotic disorder has been conceptualised as an aggregation of interacting neurodevelopmental and other insults to meet the threshold for disorder[10,11] Such insults may include a variety of risk factors implicated in the pathway to psychosis experienced throughout childhood and adolescence including genetic and familial risk, birth trauma, winter birth and childhood trauma[12,13,14]

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