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CBDMental healthSchizophrenia

CBD as a Complementary Therapy in Schizophrenia


– PhD

Affiliations : The Douglas Institute, McGill, Canada

Journal reference: DOI: 10.1176/appi.ajp.2017.17030325

Summary: Psychosis is a condition that affects the way the brain processes information and perceives reality. Patients on antipsychotic medication sometimes do not notice any improvements. In this article the potential of using CBD – one of the components of marijuana – as a treatment for psychosis is explored, with promising results.

Introduction: A cannabis compound could reduce psychotic-like symptoms in schizophrenia

One of the main forms of treatment for psychoses such as schizophrenia are antipsychotic medications. While antipsychotics help many individuals with schizophrenia, up to one-third of patients do not show any signs of improvement in symptoms, motivating new lines of treatment. Additionally, many antipsychotics induce side-effects such as weight-gain, negatively impacting other aspects of physical health and increasing the risk of heart disease. Schizophrenia is characterized by three major types of symptoms: 

  1. “Positive symptoms” (as they add to perceptual experience), such as hallucinations and delusions, 
  2. “Negative symptoms”, such as depression and lack of motivation
  3. Cognitive symptoms that disrupt general functioning like attention. 

Recent research suggests compounds in cannabis may be effective therapies in psychiatric disorders. Cannabis contains two major compounds, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). THC is largely responsible for psychotic-like symptoms experienced after exposure to cannabis, such as anxiety and paranoia, but CBD reduces the symptoms associated with THC. This indicates CBD may serve as a potential therapy for psychoses. The researchers in this study explore if it is safe and effective to administer CBD in addition to antipsychotics in individuals with schizophrenia, hoping to further improve their conditions. 

Methods: Evaluation of all psychotic symptoms on a large european cohort of psychotic patients at different time points

Participants were enrolled at 15 hospitals in the United Kingdom, Romania, and Poland. All participants were 18-65 years old and had a diagnosis of schizophrenia or similar psychotic disorders, and all had been on antipsychotics for at least 4 weeks, with some improvement. Both male and female participants were included, with 58% of the participant group being male (no trans- or non-binary people were included in the study). At the first time point (baseline), participants were assessed for both positive and negative symptoms, general functioning, cognitive performance, medication side-effects, weight, body mass index, and waist circumference. Researchers also conducted interviews to assess substance use, and collected blood to measure markers of CBD metabolism. These same tests were repeated after 1, 2, and 6 weeks, along with clinicians’ reports on severity and improvement in condition. Safety was assessed at each visit. 

Treatment: Half the patients received 1,000 mg/day of CBD (divided between 2 doses, morning and evening), ingested orally. The other half received an identical placebo solution. 

Statistical analyses: In the analyses, the researchers accounted for age and baseline symptoms profile so results would not be attributed to these factors alone. 

Results: Reduction of positive symptoms and improvement of cognitive functions after CBD treatment

In the CBD condition compared to placebo, positive symptoms (such as delusions and hallucinations) were more reduced by the end of treatment. Participants in the CBD group were more likely to be rated as improved by clinicians than individuals in the placebo group, and they had greater improvement in speed on motor tasks. However there was no difference for negative symptoms (like depression), weight, body mass index, or waist circumference.  

Of note, participants in both conditions did report adverse effects over the course of the experiment, such as gastrointestinal issues, however they were equally present in both groups. In addition, there was no difference between the groups at baseline, indicating that differences after treatment were not simply due to initial differences in the groups. 

Take home message

The authors report they have conducted the first placebo-controlled study investigating CBD in schizophrenia. Their findings indicate 6 weeks of CBD treatment adjunctive to antipsychotic medication improved symptoms such as delusions and hallucinations and improved clinicians’ ratings of overall functioning. 

CBD in addition to traditional antipsychotics may effectively reduce symptoms associated with schizophrenia.

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