CBD and Schizophrenia: Clinical Evidence, Risks, and Research Directions

Written & posted by Ingrid Ferris

Cannabis and mental health have a complicated relationship, especially when it comes to schizophrenia. Research has linked frequent cannabis use, particularly products high in THC, with an increased risk of psychosis in some people. That can make the idea of studying a cannabis-derived compound for schizophrenia a little contradictory.

But CBD and THC aren’t the same thing. 

CBD, or cannabidiol, is a non-intoxicating compound found in the hemp and cannabis plants. Unlike THC, it doesn’t produce a “high,” and researchers have been investigating whether it could affect psychotic symptoms in a very different way. A handful of clinical trials have even looked at high-dose CBD alongside traditional antipsychotic medication.

The results are interesting, but far from definitive. CBD isn’t an established treatment for schizophrenia, and the doses and formulations used in clinical research aren’t necessarily comparable to the CBD oils you can buy online or in stores. 

So… what does the research actually say? Below, we’ll break down the evidence on CBD and schizophrenia, including how cannabis affects psychosis and cognition, what clinical trials of CBD have found, potential risks, and the major questions researchers are still trying to answer.

An important note before we dive in: Research on CBD and schizophrenia is still developing, and the studies we have don’t all point in the same direction. If you’re considering CBD while managing schizophrenia or another psychotic disorder, working with a healthcare professional who understands both your mental health treatment and cannabinoid medicine is especially important. They can help you consider potential medication interactions, THC exposure, dosing, and whether CBD is appropriate for your individual situation. CBD should never replace or change prescribed treatment without medical supervision.

Schizophrenia Symptoms and Mechanisms

Before getting into the CBD research, it helps to understand what researchers are actually measuring when they talk about improvements in schizophrenia symptoms. Symptoms are generally divided into three main groups:

• Positive Symptoms: Symptoms that add experiences that aren’t normally present, including hallucinations, delusions, and disorganized thinking or speech. “Positive” doesn’t mean good in this sense; it simply means something has been added.

• Negative Symptoms: Changes such as reduced motivation, difficulty expressing emotion, social withdrawal, and loss of interest or enjoyment in everyday activities. These are symptoms that result in a lessening of normal behavior.
• Cognitive Symptoms: Difficulties with attention, memory, learning, decision-making, and processing information. 

These distinctions matter because a treatment may improve one group of symptoms without having much effect on the other. For example, reducing hallucinations doesn’t necessarily mean someone’s memory or motivation will improve at the same time.

As for what causes schizophrenia, there isn’t one simple answer. Researchers believe genetic predisposition, differences in brain development and signaling, and environmental factors can all play a role. One area of interest is the endocannabinoid system, a signaling system involved in functions such as mood, memory, stress, and cognition. 

Because compounds in cannabis interact with or influence this system, researchers have been interested in how compounds may affect schizophrenia and whether individual cannabinoids like CBD could have different effects on the brain.

Effects of Cannabis on Mental Health and Cognition

When discussing cannabis and schizophrenia, THC is a major part of the concern. THC (tetrahydrocannabinol) is the compound primarily responsible for the intoxicating effects of cannabis, and its effects on the brain are very different from those of CBD.

In the short term, THC can impair attention, memory, coordination, and judgment. Higher doses can also cause paranoia, hallucinations, or other temporary psychotic symptoms, even in people who don’t have schizophrenia. The longer-term picture, however, is more nuanced.

Frequent cannabis use has been associated with problems involving memory, learning, and attention, although factors such as how often someone uses cannabis, THC potency, age of first use, and other substance use can all influence the outcome.

There’s also a well-established association between cannabis use and psychotic disorders. The risk appears to be greater with frequent use and high-potency cannabis, particularly among people who already have other risk factors for psychosis.

That doesn’t mean everyone who uses cannabis will develop schizophrenia, or that cannabis is the sole cause of the disorder. Genetic predisposition, environmental factors, age, frequency of use, and the type of cannabis exposure all matter.

This is also why it’s important not to use “cannabis” and “CBD” interchangeably. Much of the concern surrounding cannabis and psychosis centers on THC exposure, while researchers are studying CBD separately to understand whether it could have different effects.

CBD Pharmacology Relevant to Mental Health

CBD affects the brain differently from THC. THC strongly activates the CB1 cannabinoid receptors, which helps explain its intoxicating and psychosis-related effects. CBD doesn’t activate these receptors in the same way and appears to influence several signaling symptoms instead. 

One area researchers are particularly interested in is anandamide, a naturally occurring cannabinoid made by the body. One clinical trial found that CBD increased anandamide levels, and those increases were associated with improvements in psychotic symptoms. Researchers have also studied CBD’s effects on serotonin, dopamine, and other signaling pathways, but they’re still trying to figure out how these mechanisms might relate to schizophrenia.

The doses used in schizophrenia research are also important. Human trials have typically tested hundreds of milligrams of oral CBD per day, including studies using 600, 800, and 1,000 mg daily. These amounts are much higher than what someone might casually take from consumer CBD oil, so clinical trial results shouldn’t automatically be applied to everyday CBD use. 

Additionally, CBD can affect enzymes in the liver that process medications. This creates the potential for drug interactions, including with some medications used for mental health conditions. For someone taking antipsychotic medication, this relationship is especially important. CBD shouldn’t be added to a schizophrenia treatment plan without discussing it with the prescribing psychiatrist or another healthcare provider.

Cannabis Use in Patients with Schizophrenia

Cannabis use is relatively common among people with schizophrenia and other psychiatric disorders. Estimates vary depending on the population being studied, but research has consistently found higher rates of cannabis use disorder among people with schizophrenia than in the general population.

Why someone uses cannabis can vary just as much. Some report using it recreationally or socially, while others describe using cannabis to relax, sleep, cope with stress, or manage unpleasant emotions and symptoms. This idea is sometimes called the self-medication hypothesis.

But feeling temporary relief doesn’t necessarily mean cannabis is improving the underlying condition. In people who have already experienced psychosis, continued cannabis use has been associated with a greater risk of relapse and longer hospital stays. Research has also found an association between cannabis and poor medication adherence, which can further complicate treatment. 

Again, THC content matters. Using high-THC cannabis isn’t the same as taking purified CBD in a clinical trial, which is why it’s important to separate research on cannabis use from research on CBD treatment. 

For people with schizophrenia or schizoaffective disorder, cannabis use shouldn’t be viewed as a harmless form of self-treatment. Its effects can vary between individuals, and THC exposure may be particularly risky for someone who’s already vulnerable to psychosis.

Clinical Evidence: CBD Trials and Symptom Scales

So, has CBD actually improved schizophrenia in human trials? Some studies have found promising results, while others haven’t found a meaningful benefit. Three clinical trials help show why the evidence is still considered to be in the early stages:

Study	CBD Treatment	What Researchers Found
Leweke et al.	Up to 800 mg/day for 4 weeks	CBD and the antipsychotic amisulpride both improved symptoms, with CBD causing fewer side effects in the study
McGuire et al.	1,000 mg/day for 6 weeks alongside antipsychotic medication	CBD was associated with a greater reduction in positive symptoms than placebo
Boggs et al.	600 mg/day for 6 weeks alongside antipsychotic medication	CBD did not significantly improve overall schizophrenia symptoms or cognitive performance compared with placebo

These trials have also measured different outcomes. Researchers commonly use the Positive and Negative Syndrome Scale (PANSS) to track changes in symptoms such as hallucinations, delusions, social withdrawal, and reduced emotional expression. Cognitive tests may separately measure memory, attention, processing speed, and other thinking skills. 

The McGuire trial is particularly notable because it included 88 participants across multiple centers. Those receiving CBD alongside their existing medication had a modest but statistically significant improvement in positive symptoms compared with placebo. However, significant improvements weren’t found across every symptom or cognitive measure.

Meanwhile, the Boggs trial found no additional improvement in PANSS scores or cognition with 600 mg of CBD per day. 

Taken together, the findings suggest CBD is worth further study, but they don’t establish it as a treatment for schizophrenia. The trials have been relatively small, used different doses and designs, and produced mixed results.

Cross-Over Trial: Acute CBD Pre-treatment Studies

A more recent cross-over trial adds an important nuance to the research. Instead of asking whether CBD could improve schizophrenia symptoms on its own, Chesney and colleagues asked whether taking CBD before cannabis could reduce some of THC’s effects.

The 2025 study included 30 people with schizophrenia or schizoaffective disorder who also had cannabis use disorder. Each participant received either 1,000 mg of oral CBD or a placebo three hours before using cannabis containing THC. Because it was a crossover study, participants completed both conditions at different visits, allowing researchers to compare their responses.

The results weren’t necessarily what researchers expected.

After CBD pre-treatment, participants performed worse on a delayed verbal memory test than they did after placebo. CBD also didn’t protect against positive psychotic symptoms. Instead, PANSS positive-symptom scores increased more after cannabis when participants had received CBD beforehand. Both differences were statistically significant.

Researchers also measured THC and its metabolites in the blood. CBD didn’t significantly increase exposure to THC or its active metabolite, suggesting the results couldn’t simply be explained by CBD causing participants to have more THC in their symptoms. 

These findings don’t prove that CBD worsens schizophrenia. This was a small, specific group who already used cannabis regularly, and researchers were testing CBD combined with THC rather than CBD as a standalone treatment. 

What the study does show is that CBD shouldn’t be assumed to cancel out THC’s effects or make cannabis safer for people with schizophrenia.

Negative Syndrome Scale and Other Symptom Measures

When researchers say schizophrenia symptoms “improved,” it’s important to know what they actually measured. One of the most common tools is the Positive and Negative Syndrome Scale (PANSS). It includes 30 items covering positive symptoms, negative symptoms, and general symptoms such as anxiety and depression. Researchers may look at a total score or individualized sections depending on what they’re studying.

Negative symptoms can also be measured with tools such as the Scale for the Assessment of Negative Symptoms (SANS). These scales look at symptoms like reduced emotional expression, social withdrawal, and lack of motivation.

So far, CBD’s effects on negative symptoms haven’t been particularly convincing. In the McGuire multicenter randomized controlled trial, 1,000 mg of CBD per day produced a statistically significant improvement in positive psychotic symptoms compared with placebo. However, differences in negative symptoms measured with PANSS and SANS weren’t statistically significant.

That distinction matters. A treatment that affects hallucinations or delusions isn’t necessarily improving motivation, social functioning, memory, or other challenges associated with chronic schizophrenia. Using standardized measures consistently in future human trials would also make CBD studies easier to compare.

Adverse Events and Adverse Effects

Even if CBD eventually proves useful for some people with schizophrenia, safety is a major part of the equation, especially when it’s being taken alongside antipsychotic medication.

So far, CBD has generally been well tolerated in small clinical trials involving people with schizophrenia. In the McGuire trial, adverse events occurred at similar overall rates in the CBD and placebo groups. Gastrointestinal problems were more common among participants taking CBD, with diarrhea and nausea among the reported issues. Most adverse events in both groups were mild and resolved without treatment.

Other CBD research has reported adverse effects such as sedation and changes in liver enzymes, particularly at higher doses or when CBD is combined with certain medications. Drug interactions are a particular concern. Because CBD can affect liver enzymes processing medications, researchers have noted that some schizophrenia trials didn’t measure blood levels of participants’ antipsychotics. That makes it difficult to completely rule out interactions between CBD treatment and existing medications.

For anyone considering CBD, monitoring should go beyond simply asking whether symptoms feel better. A healthcare provider may want to review current medications and establish baseline health information before CBD exposure, then monitor for new symptoms, side effects, or other clinically relevant changes.

Guidance for Patients With Schizophrenia on CBD and Cannabis Use

The biggest takeaway from the research is that CBD and cannabis shouldn’t be treated as interchangeable. 

For people with schizophrenia or other schizophrenia spectrum disorders, THC-containing cannabis is the bigger concern. THC can cause acute psychotomimetic symptoms, including paranoia and altered perception, and frequent use of high-potency cannabis strains has been associated with a greater risk of psychosis. 

That risk is especially important for people who have already experienced psychosis or may be vulnerable to developing schizophrenia. CBD shouldn’t be assumed to make a THC-containing product safer, either. As the Chesney cross-over trial showed, CBD pre-treatment didn’t prevent related memory impairment or positive psychotic symptoms in participants with schizophrenia or schizoaffective disorder. 

Anyone currently being treated for schizophrenia should talk with their psychiatrist before trying CBD. The high-dose cannabidiol treatment studied in clinical trials is very different from casually adding a consumer CBD product to your routine, and CBD may interact with medications.

If CBD is used with a clinician’s guidance, keeping a simple symptom log can help track changes in sleep, mood, anxiety, cognitive functioning, psychotic symptoms, medication side effects, and any other noticeable changes.

And most importantly: CBD should never be used as a reason to stop or reduce prescribed antipsychotic medication without supervision. At this point, research supports studying CBD as a possible adjunctive therapy, not replacing established schizophrenia treatment.

Research Gaps and Future Cross-Over Trial Needs

CBD has generated enough interest to justify more research, but the evidence isn’t strong enough to call it a novel treatment for schizophrenia yet.

One of the biggest limitations is simply size. Existing human trials have generally included relatively small groups of patients with schizophrenia, and studies have differed in CBD dose, duration, participant characteristics, and the outcomes they measure. Larger randomized clinical trials could give researchers a much clearer picture.

Future studies should also use consistent designs and measurements. A well-designed double-blind, placebo-controlled trial could track positive and negative symptoms alongside cognitive outcomes, daily functioning, medication levels, and adverse effects. Using the same measures across studies would make the results easier to compare in future systematic reviews. 

Researchers also need to better understand who they’re studying. Trials involving people with cannabis use disorder answer different questions than trials involving people who don’t regularly use cannabis. Both groups are important, but their results shouldn’t automatically be treated as interchangeable. 

Future crossover studies should also examine the individual and combined effects of CBD and THC while measuring both drug levels and changes in symptoms. This could help clarify whether CBD affects psychosis reactivity, memory, or other acute effects of THC differently depending on dose and participant characteristics.

Finally, adverse events need to be reported consistently. Better monitoring of medication interactions, cognitive functioning, and other acute adverse effects would help researchers understand not only whether CBD works, but for whom it can be studied safely.

For now, the mixed findings are exactly why larger, carefully controlled studies are still needed.

Explore High-Quality CBD From Myriam’s Hemp

CBD research in schizophrenia is still evolving, and the mixed findings are exactly why this isn’t an area for trial and error. If you’re interested in CBD, work with your psychiatrist or a healthcare professional knowledgeable about cannabinoid medicine to determine whether it makes sense alongside your current treatment plan.

If CBD is appropriate for you, product quality matters, too. At Myriam’s Hemp, we make it easy to know what you’re getting with transparent ingredients and third-party lab testing. Explore our CBD products to find an option that fits your needs, and bring the product information and Certificate of Analysis to your healthcare provider so you can make an informed decision together.