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 x 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.
| Original language | English |
|---|---|
| Pages (from-to) | 1-19 |
| Number of pages | 24 |
| Journal | NPJ SCHIZOPHRENIA |
| Publication status | Accepted/In press - 9 Apr 2021 |