Gone to Pot – A Review of the Association between Cannabis and Psychosis

Abstract

Cannabis is the most commonly used illicit drug worldwide, with ~5 million daily users worldwide. Emerging evidence supports a number of associations between cannabis and psychosis/psychotic disorders, including schizophrenia. These associations-based on case-studies, surveys, epidemiological studies, and experimental studies indicate that cannabinoids can produce acute, transient effects; acute, persistent effects; and delayed, persistent effects that recapitulate the psychopathology and psychophysiology seen in schizophrenia. Acute exposure to both cannabis and synthetic cannabinoids (Spice/K2) can produce a full range of transient psychotomimetic symptoms, cognitive deficits, and psychophysiological abnormalities that bear a striking resemblance to symptoms of schizophrenia. In individuals with an established psychotic disorder, cannabinoids can exacerbate symptoms, trigger relapse, and have negative consequences on the course of the illness. Several factors appear to moderate these associations, including family history, genetic factors, history of childhood abuse, and the age at onset of cannabis use. Exposure to cannabinoids in adolescence confers a higher risk for psychosis outcomes in later life and the risk is dose-related. Individuals with polymorphisms of COMT and AKT1 genes may be at increased risk for psychotic disorders in association with cannabinoids, as are individuals with a family history of psychotic disorders or a history of childhood trauma. The relationship between cannabis and schizophrenia fulfills many but not all of the standard criteria for causality, including temporality, biological gradient, biological plausibility, experimental evidence, consistency, and coherence. At the present time, the evidence indicates that cannabis may be a component cause in the emergence of psychosis, and this warrants serious consideration from the point of view of public health policy.

Cannabinoids and Schizophrenia: Risks and Therapeutic Potential

“…An analysis of results from 35 studies revealed a pooled odds ratio of 1.4 for risk of developing psychosis in individuals with any history of cannabis exposure and an odds ratio of 2.1 among individuals with histories of more frequent use [7]. In addition, a relationship between the age of initiation of cannabis use and age of onset of psychosis has also been well documented, with most studies finding that cannabis use precedes onset of psychosis and that the amount of cannabis exposure in adolescence may be the strongest determinant of this association [4]. However, several issues have complicated interpretation of these findings, including the role of comorbid substance use, of male sex (which is associated with higher rates of cannabis use and earlier age of onset of schizophrenia), of lower socioeconomic status, and of the potentially poor reliability of self-reported histories of past cannabis use.…”

“…Arguing in support of a causal relationship is the consistently replicated evidence in different populations that cannabis use precedes psychotic symptoms [20,21], there is a dose effect [16], and there are coherent, plausible biological mechanisms [4,22,23].…”

“…Cannabis sativa is the most commonly used illicit substance globally, and its main psychoactive component, Δ 9 -tetrahydrocannabinol (THC), has been widely recognized for its ability to cause acute psychotic symptoms and cognitive impairment similar to schizophrenia [3,4]. Cannabis is also the most commonly abused illicit substance amongst people with schizophrenia, and there is substantial evidence that continued use after a schizophrenia diagnosis is associated with worsening psychotic symptoms, relapse, and decreased functioning over time [4,5].…”

“…Cannabis is also the most commonly abused illicit substance amongst people with schizophrenia, and there is substantial evidence that continued use after a schizophrenia diagnosis is associated with worsening psychotic symptoms, relapse, and decreased functioning over time [4,5]. Furthermore, epidemiologic evidence has accumulated implicating cannabis use as an important environmental risk factor for developing schizophrenia.…”

Predicting First-Episode Psychosis Associated with Cannabis Use with Artificial Neural Networks and Deep Learning

“…On the other hand evidence shows that the increase in cannabis consumption is proportionate to the increase in the proportion of people seeking treatment for psychotic disorders [1]. While there is some evidence that consuming cannabis is a risk factor for several types of psychotic disorders [2], the link between these two factors needs to be better quantified. These days, researchers attempted to understand whether specific patterns of cannabis use such as potency or age are associated with a higher risk of developing psychotic disorders.…”