Cannabidiol as an adjuvant therapy in schizophrenia: multicenter RCT

Introduction and clinical context

The study Cannabidiol as an adjuvant therapy in schizophrenia: multicenter RCT (Am J Psychiatry · 2018) is part of the scientific research on the use of cannabinoids in schizophrenia and psychosis.

It is important to differentiate the components of cannabis: while THC, in recreational use and at high doses, is associated with psychotic risk, cannabidiol (CBD) has been investigated for a possible antipsychotic effect. Clinical trials evaluated CBD as an adjuvant therapy in schizophrenia, with signs of symptom reduction and a good tolerability profile in some studies. The area is promising, but still consolidating, and psychiatric management remains essential.

Understanding what science shows about the use of cannabinoids in schizophrenia and psychosis helps patients and healthcare professionals make safer, well-founded decisions, based on evidence rather than common sense.

Methodology and findings

This clinical trial was conducted in a controlled manner, comparing the treatment with a reference group. RCT (McGuire et al.): CBD 1000 mg/day reduced positive psychotic symptoms vs placebo, with good tolerability. The blinded, controlled design reduces bias and increases the reliability of the finding. Results from controlled trials like this are especially valuable for guiding therapeutic decisions.

Mechanism of action and safety

Here the distinction between the cannabinoids is crucial: THC, a CB1 receptor agonist, can precipitate or worsen psychotic symptoms, while CBD has a distinct pharmacological profile, investigated for a possible antipsychotic effect via modulation of signaling and of serotonergic receptors. On safety, CBD is usually well tolerated, but attention is given to drug interactions and to the need to maintain the baseline psychiatric treatment. Recreational use of THC-rich cannabis is advised against in this population due to the risk of decompensation.

Regulation in Brazil (Anvisa)

In Brazil, access to cannabis products is regulated by Anvisa — mainly through RDC 660/2022 (patient import with a medical prescription) and the new manufacturing and import framework, RDC 1,015/2026. Any therapeutic use must start from an individualized medical assessment and prescription. This content is informative and scientific and does not replace the guidance of a healthcare professional.

This is informative content produced by Brazcann; for the full methodology and detailed results, consult the original publication (Am J Psychiatry · 2018). Access to cannabis treatments must always occur through the regulated pathway, with a prescription and medical follow-up.

Frequently asked questions

Is CBD different from THC in psychosis?

Yes. THC can increase psychotic risk; CBD is investigated for a possible antipsychotic effect.

Does CBD treat schizophrenia?

It was studied as an adjuvant therapy with positive signs; the evidence is still consolidating.