CBD LoveThe independent Australian guideSearch

CBD for psychosis and schizophrenia

A few small trials of high-dose CBD (600 to 1,000 mg a day) in schizophrenia gave mixed results. THC, unlike CBD, can trigger or worsen psychosis.

Facts checked 13 November 20265 min readHow we research
Limited evidence

A few small randomised trials at 600 to 1,000 mg a day, mostly as an add-on to antipsychotic medicine, with mixed results.

How we grade evidence

CBD is not a proven treatment for psychosis or schizophrenia. A few small trials have tested high prescription doses, mostly added to antipsychotic medicine, and the results were mixed. CBD must be kept separate from THC here, because THC can trigger or worsen psychosis.

What the research shows

Psychosis means losing touch with reality, for example hearing voices or holding fixed false beliefs. Schizophrenia is a long-term condition in which psychosis is a main feature.

The individual trials

Trial Who CBD dose Result
Leweke 2012 42 acutely unwell patients Up to 800 mg a day for 4 weeks, compared with the antipsychotic amisulpride (no placebo group) Symptoms improved by a similar amount in both groups, with fewer side effects on CBD1
McGuire 2018 88 people (43 CBD, 45 placebo) 1,000 mg a day for 6 weeks, added to antipsychotics Modest improvement in positive symptoms2
Boggs 2018 36 outpatients with chronic schizophrenia 600 mg a day for 6 weeks, added to antipsychotics No improvement in symptom scores or thinking skills compared with placebo. Sedation was more common with CBD3

“Positive symptoms” are things like hallucinations and delusions. “Negative symptoms” are things like loss of motivation and withdrawal from other people.

In the Boggs trial, thinking skills improved over time only in the placebo group.3

The pooled evidence

  • A 2026 meta-analysis (a study that pools trials) of five randomised trials found a small but statistically significant advantage for add-on CBD on total, positive and general symptoms. It found no advantage on negative symptoms.4
  • A 2026 review in The Lancet Psychiatry looked at all cannabinoids together, including products with THC, across 54 trials. It found no significant effect on outcomes in psychotic disorders.5

Put together: there is a possible small effect at high doses, seen in a handful of small and short trials. That is why the grade is “limited evidence”. See how we grade the evidence.

What doses were tested

The trials used 600 to 1,000 mg of CBD a day.123 The one clearly negative trial used the lowest of these doses, 600 mg.3

The limit for pharmacist-only (Schedule 3) CBD in Australia is 150 mg a day.6 No trial has tested doses in that range for psychosis. The evidence that exists applies only to high prescription doses given under psychiatric care.

What Australian medical bodies say

  • RANZCP. The Royal Australian and New Zealand College of Psychiatrists updated its clinical memorandum in March 2024. It says there is insufficient evidence to support medicinal cannabis as a treatment for mental disorders, raises concern about overprescribing, and flags the risk of psychosis with high-potency THC products.7
  • RACGP. The Royal Australian College of General Practitioners does not recommend or encourage the use of medicinal cannabis, and says it should only be considered after first-line, evidence-based treatments have been exhausted.8

See what Australian medical bodies say about CBD.

Risks to know about

  • THC. THC can trigger or worsen psychosis.7 For anyone with a history of psychosis, the THC content of a product is the main safety question. See CBD vs THC and who should not take CBD.
  • Mislabelled products. Products bought outside the prescription system may not match their labels. In a US study of 84 CBD products bought online, only 31% were accurately labelled, and some contained THC.9 Products supplied on prescription in Australia and tested by the TGA were mostly close to their labels.10 See is what is on the label in the bottle?.
  • Sedation. Sedation was more common with CBD than placebo in the Boggs trial.3 CBD also adds to the drowsiness caused by other sedating medicines.11
  • Interactions. CBD blocks several liver enzymes that break down other medicines.11 Ask your psychiatrist or pharmacist to check it against your current medicines. See CBD drug interactions.
  • Liver. In a study of healthy adults taking about 350 to 400 mg of CBD a day for four weeks, 5.6% had liver enzymes rise to more than three times the normal upper limit.12 The psychosis trials used higher doses than that. See CBD and the liver.
  • Stopping medicine. No trial supports replacing antipsychotic medicine with CBD.

If you are considering it

  • Talk to your psychiatrist or GP first, and do not change your current medicine on your own.
  • If you use any cannabis product, tell your treating team exactly what it is and whether it contains THC.
  • Questions worth asking about any treatment suggested: How would it interact with my medicines? What monitoring would I need? How will we judge whether it is working?

Footnotes

  1. Leweke FM, et al. Cannabidiol enhances anandamide signaling and alleviates psychotic symptoms of schizophrenia. Translational Psychiatry, 2012. https://pmc.ncbi.nlm.nih.gov/articles/PMC3316151/ ↩ ↩2

  2. Review of cannabidiol trials in psychosis, including McGuire et al., 2018. https://pmc.ncbi.nlm.nih.gov/articles/PMC8005219/ ↩ ↩2

  3. Boggs DL, et al. The effects of cannabidiol (CBD) on cognition and symptoms in outpatients with chronic schizophrenia: a randomized placebo controlled trial. Psychopharmacology, 2018. https://doi.org/10.1007/s00213-018-4885-9 ↩ ↩2 ↩3 ↩4 ↩5

  4. Meta-analysis of five randomised trials of adjunctive cannabidiol in schizophrenia, 2026. https://pubmed.ncbi.nlm.nih.gov/42047775/ ↩

  5. Wilson J, et al. Cannabinoids for mental disorders: systematic review and meta-analysis. The Lancet Psychiatry, 2026. https://pubmed.ncbi.nlm.nih.gov/41856154/ ↩

  6. Therapeutic Goods Administration. Final decision on down-scheduling of low-dose cannabidiol, 2020. https://tga.gov.au/node/284859 ↩

  7. Royal Australian and New Zealand College of Psychiatrists. Updated clinical memorandum: therapeutic use of medicinal cannabis, March 2024. https://ranzcp.org/news-analysis/updated-clinical-memorandum-therapeutic-use-of-medicinal-cannabis ↩ ↩2

  8. Royal Australian College of General Practitioners. Position statement: use of medicinal cannabis products in Australia (2019 update). https://www.racgp.org.au/advocacy/position-statements/view-all-position-statements/clinical-and-practice-management/medical-cannabis ↩

  9. Bonn-Miller MO, et al. Labeling accuracy of cannabidiol extracts sold online. JAMA, 2017. https://jamanetwork.com/journals/jama/fullarticle/2661569 ↩

  10. Therapeutic Goods Administration. Testing of medicinal cannabis products being supplied under the Special Access Scheme in Australia. https://www.tga.gov.au/resources/publication/tga-laboratory-testing-reports/testing-medicinal-cannabis-products-being-supplied-sas-australia ↩

  11. US National Library of Medicine, DailyMed. Epidiolex (cannabidiol) oral solution prescribing information, revised 2026. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8bf27097-4870-43fb-94f0-f3d0871d1eec ↩ ↩2

  12. EurekAlert. News release on Florian et al., cannabidiol and liver enzyme elevations in healthy adults, JAMA Internal Medicine, July 2025. https://www.eurekalert.org/news-releases/1089832 ↩

Common questions

Does CBD help schizophrenia?

It is not proven. A few small trials have tested 600 to 1,000 mg a day, mostly added to antipsychotic medicine, and the results were mixed. One found a modest improvement in symptoms and another found no improvement.

Can CBD cause psychosis?

THC, the compound in cannabis that causes a high, can trigger or worsen psychosis. CBD is a different compound and has been studied as a possible treatment, with mixed results. The practical risk is that a product sold as CBD may also contain THC.

Can I use CBD instead of antipsychotic medication?

No trial supports that. Most trials added CBD to people's existing antipsychotic medicine. Any change to antipsychotic medicine should be made with your psychiatrist.

What dose of CBD was used in schizophrenia trials?

The trials used 600 to 1,000 mg a day, which is four to nearly seven times the 150 mg a day limit for pharmacist-only CBD in Australia. There is no evidence for low doses in psychosis. A prescriber sets the dose of any prescribed product.

This page is general information, not medical or legal advice. Laws and evidence change; we show the date we last checked the facts at the top of every page. Talk to your doctor or pharmacist before starting, stopping or changing any medicine.

Didn't find what you needed? Ask us a question.

Keep reading