Cannabis

This podcast contains information about cannabis. Here we explain what cannabis is, its legal status, its effects on the brain and body, and its use as a treatment.

November 2020

Last updated at: 1:53 am, 1st February 2021

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What are endocannabinoids? The endocannabinoid system is an endogenous biological system that regulates functions including cognition, sleep, energy metabolism, and inflammation. It modulates different neurotransmitter systems in the brain, including dopamine, glutamate, and GABA using two major lipid-based mediators, anandamide and arachidonoyl-sn-glycerol, that act through type one and type two cannabinoid receptors. Exogenous cannabinoids, such as delta-9-tetrahydrocannabinol (THC), the main psychoactive components of cannabis, and cannabidiol (CBD), impact on the endocannabinoid system. While disturbance of the endocannabinoid system after cannabis consumption has been associated with increased risk of psychotic illness, CBD alone has shown anti-inflammatory and antipsychotic properties. What is…

Drug and alcohol use

What is substance use in bipolar disorder? Substance use is a concern for people with a mental illness due to the association with poor clinical and social outcomes. Substance use places additional burden on patients, families, psychiatric services, and government resources due to high rates of treatment non-adherence and relapse. Substance abuse leads to risk-taking behaviour, illegal activity, interpersonal problems and a loss of interest in usual activities. Abuse jeopardises physical health and neglect of important commitments at home, school or work. Substance dependence involves having a strong physical or psychological need for the substance. Not taking it leads to…

Substance use

How is substance use related to bipolar disorder? Various lines of evidence suggest an association between substance use and psychiatric disorders. In particular, use during adolescence or early adult life is now thought to be one of a number of environmental stressors that interact with genetic factors to predispose an individual to later bipolar disorder. What is the evidence for substance use as a risk factor for bipolar disorder? Moderate quality evidence suggests a medium to large effect of increased risk of bipolar disorder with prior cannabis use and a small to medium-sized effect of increased risk of bipolar disorder…

Cannabidiol

What is cannabidiol? The plant cannabis sativa contains over 70 different constituents, including tetrahydrocannabinol (THC) and cannabidiol (CBD), which are the most concentrated substances found in cannabis extracts. Recreational cannabis use during adolescence is a well documented risk factor for schizophrenia, particularly cannabis with high THC content. While THC induces symptoms in healthy volunteers that resemble psychosis, CBD interferes with the detrimental actions of THC in terms of psychotic proneness. Therefore, there is potential for CBD to act as an antipsychotic agent. What is the evidence for cannabidiol? Moderate to low quality evidence is unable to determine the benefits of…

Medicinal cannabis

What is medicinal cannabis for schizophrenia? Countries are increasingly allowing cannabinoids (tetrahydrocannabinol [THC] and cannabidiol [CBD]) to be made available for medicinal purposes, including for the treatment of mental disorders. Medicinal cannabis refers to any part of the cannabis plant, such as flowers, buds, leaves, or full plant extracts. Pharmaceutical cannabinoids refer to pharmaceutical-grade medicinal extracts with defined and standardised THC, CBD, or a combination of both, and synthetic cannabinoid derivatives. What is the evidence for cannabinoids for schizophrenia? Moderate to low quality evidence finds no improvement in overall and positive symptoms with adjunctive CBD or THC compared to placebo….

Substance use

How is substance use related to schizophrenia? Various lines of evidence suggest an association between substance use and psychosis. Experimental studies and surveys of users provide evidence that cannabis and amphetamine use can produce transient, and usually mild, psychotic experiences or recurrence of psychotic symptoms in individuals with a history of psychosis. Further, neuroimaging studies have found clear similarities between functional networks impaired by cannabis use and those known to be implicated in the pathogenesis of schizophrenia. What is the evidence for substance use as a risk factor for schizophrenia? Tobacco Moderate quality evidence finds a small to medium-sized increased…

Drug and alcohol use

What is comorbid drug and alcohol use? Drug and alcohol misuse, abuse or dependence are concerns for people with schizophrenia due to the association with poor clinical and social outcomes, including high rates of suicide, HIV, homelessness, aggression and incarceration. Moreover, substance use places additional burden on patients, families, psychiatric services, and government resources due to high rates of treatment non-adherence and relapse. This topic covers outcomes for people with schizophrenia and comorbid substance use (termed ‘dual diagnosis’). Please also see the topic on rates of comorbid substance use, as well as substance use as a risk factor for schizophrenia. What…

Cannabis

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