Summary
Objectives: Cannabis is the most widely used illicit drug globally and its use
has been linked to an increased risk for psychotic disorders. An association
between cannabis consumption and psychotic symptoms was consistently reported
by several studies. This case-control study aimed to widen the current
findings about the impact of cannabis exposure on the risk of psychosis, by
investigating the pattern of cannabis consumption in a sample of first-episode
of psychosis (FEP) patients compared to healthy controls.
Material and methods: 68 individuals who presented for the first time to mental
health services of Palermo (Italy) with an ICD-10 diagnosis of psychotic disorders
and 74 healthy were enrolled as part of the Sicilian Genetics and Psychosis
study. Psychopathological assessment and diagnosis were carried out by
the Schedule for Clinical Assessment in Neuropsychiatry (SCAN). Socio-demographic
data were collected by the modified version of the Medical Research
Council (MRC) socio-demographic scale. All participants were interviewed using
the Cannabis Experience Questionnaire \u2013 Modified Version to obtain a detailed
assessment of lifetime patterns of cannabis and other illicit drug consumption.
Logistic regression was applied to investigate the relationships between various
aspects of cannabis use (lifetime use, age at first use, duration, and frequency of
use) and case-control status while controlling for potential confounders.
Results: Patients started cannabis consumption about 3 years earlier than
the control group (t = 3.1, p = 0.002) and were 8 times more likely to having
started using cannabis before 15 years (adjusted OR = 8.0, 95% CI 2.4-27)
than controls. Furthermore cases were more likely to smoke more frequently
than controls (adjusted OR = 4.4, 95% CI 1.08-18). We did not find a difference
in duration of cannabis use between cases and controls.
Conclusions: The findings suggest that cannabis exposure, and especially
daily cannabis consumption, is associated with the risk for psychosis; however,
the retrospective study design does not allow drawing firm conclusions about
causality