Evidence based

CBD and Schizophrenia: Current Research & Understanding

Schizophrenia spectrum disorders are a group of neurological conditions affecting the perception of reality and cognition. There is no cure, but CBD has been shown to be beneficial for several aspects of the condition.

Article By
Justin Cooke , posted 3 months ago

“Schizo” means “split,” and “phrenia” means “of the mind” in Greek — therefore, schizophrenia is described as a “splitting of the mind.”

Rather than referring to split personality disorder (which it is not), the term relates to fragmentation of thoughts — a split from reality.

Schizophrenia causes disordered thoughts and speech, visual or auditory hallucinations, and a myriad of other symptoms that can vary from one person to the next. There’s no cure for this condition; however, with treatment, those affected may go on to live otherwise normal, independent lives. Medical researchers are continually looking for new, effective treatment options for schizophrenia, and in recent years have turned their focus toward CBD — a powerfully medicinal (non-psychoactive) compound contained in the cannabis plant.

In this article, we’ll discuss what we know about this debilitating mental health condition and how CBD can be used to support treatment after a diagnosis of schizophrenia.

  • Table of Contents

Summary: Using CBD for Schizophrenia

Schizophrenia is a complex neurological disorder involving many different confounding factors working together to produce symptoms. This means that there is no single effective treatment for the disorder. Successful treatment, therefore, requires an all-encompassing approach. Everything from changes in diet and lifestyle to supplements and medications should be combined to manage the condition.

CBD has been shown to offer some unique benefits that may be combined with other treatments to maximize the management of the disorder. The mechanism of action for CBD remains unclear, however.

The Suggested Mechanisms of CBD for Schizophrenia Include:

  • Vanilloid receptor activation (TRPV1)
  • Modulation of neurotransmitters — dopamine, serotonin, and glutamate
  • Increased blood flow to cortical regions of the brain
  • Improvements in common side-effects of schizophrenia — cognitive deficits, anxiety, depression, and insomnia

What is Schizophrenia?

Schizophrenia is an umbrella term for a group of chronic brain disorders involving delusions, hallucinations, difficulty staying focused, and lack of motivation. It’s a rare condition, affecting less than 1% of the population, according to the American Psychiatric Association.

There are a lot of misconceptions in public understanding of this condition. Despite popular belief, most schizophrenics aren’t dangerous. They don’t live in hospitals or have split personalities. Most people who have the condition can live reasonably normal lives — they often have jobs and families, and most of them can live independently.

Schizophrenia affects both men and women equally, but symptoms tend to appear sooner in males than females. Men usually begin experiencing symptoms around their late-teens to early 20s, while females typically start showing signs in their late 20s or early 30s. It’s extremely rare for anybody under the age of 12 to show symptoms of schizophrenia.

Schizophrenia itself isn’t deadly, but it’s often associated with other medical conditions that can lead to problems later in life — such as heart disease or diabetes.

Three Phases of Schizophrenia

1. Prodromal Phase

This is the phase leading up to the first display of schizophrenic symptoms. If detected early enough, the onset and severity of schizophrenia can be significantly reduced.

In the prodromal phase, patients often experience nonspecific clinical symptoms such as depression, anxiety, social isolation, and learning disabilities.

The prodromal phase can last anywhere from several weeks to several years [1].

2. Active Phase

During this phase, symptoms become more severe, involving delusions, hallucinations, and catatonic behavior. This is when treatment is most important and when most schizophrenia diagnoses are made.

3. Residual Phase

In the residual phase, symptoms may begin to disappear, but patients are often left feeling “flat,” with poor motivation, low mood, and inability to focus or concentrate. Treatment during this phase is still important but tends to be more directed toward mood disorders.

Symptoms of Schizophrenia

The symptoms of schizophrenia can be divided into three main categories:

A) Positive (Psychotic) Symptoms

  • Delusions
  • Hallucinations
  • Disorganized speech
  • Disorganized behavior
  • Catatonic behavior
  • Psychosis

B) Negative Symptoms

  • Changes in emotions
  • Flat affect
  • Lack of detail in speech (Alogia)
  • Loss of motivation (Avolution)

C) Cognitive Symptoms

  • Poor memory
  • Learning difficulties
  • Poor concentration

Causes of Schizophrenia

Unfortunately, there isn’t a single cause of schizophrenia. Research has linked the disorder with some different potential causes, including environmental influences, changes in brain chemistry, and physical or emotional trauma.

1. Dopamine Theory

One of the leading theories for the causes of schizophrenia comes from the mechanism many of the effective antipsychotic drugs use. A lot of these medications work by blocking dopamine (D2) receptors in the brain — suggesting that schizophrenia is caused by too much dopamine in the brain.

However, this is often disputed because symptoms of schizophrenia often mimic other conditions such as ADHD and Parkinson’s disease, which are conversely thought to be caused by low dopamine.

2. Brain Structure Abnormality Theory

Neuroimaging studies have shown that patients with differing symptoms have abnormalities (such as reduced blood flow) in different areas of the brain.

For example, patients experiencing hallucinations have been shown to have abnormalities in the thalamus — the area of the brain tasked with filtering and processing sensory signals such as sight, sound, or touch. Other studies have found that patients experiencing paranoia often have abnormalities in the amygdala — which is associated with processing fear.

All of these different factors suggest that schizophrenia can be caused by dysfunctions in many different areas of the brain. Symptoms will be determined by the part of the brain that is most affected.

Low doses of cannabis improve blood flow to regions of the brain involved with regulating mood, perception, and mood — potentially reducing psychotic symptoms associated with schizophrenia [10].

3. Glutamate Theory

Glutamate is the most abundant neurotransmitter in the brain. One theory regarding schizophrenia involves excessive glutamate activity in the brain. This theory could be used to explain many of the symptoms associated with the condition. Additionally, the psychoactive drug phencyclidine (PCP) — known for producing schizophrenic-like psychosis — produces its activity through activation of the glutamate receptors in the brain [8].

This has led some medical researchers to suggest schizophrenia involves similar overactivation of glutamate.

Studies show that synthetic cannabinoids reduce PCP-induced schizophrenic symptoms in rats [9].

4. Anandamide Excess Theory

Other research findings suggest schizophrenic patients have significantly higher levels of anandamide [4]. Similar studies report dysfunctional CB1 receptor activity in schizophrenic patients, especially in regions of the brain relating to cognition and memory — two functions highly compromised in schizophrenia [5, 6].

Patients with abnormal anandamide levels as a primary cause for their symptoms are the most likely to be negatively affected by THC — which is a well-known CB1 receptor agonist [7].

This, of course, makes schizophrenia challenging to treat because there are so many different factors to take into account. It also explains why some patients respond to treatment, and others don’t.

Some Suggested Causes of Schizophrenia Include:

  • Severe or long-term stress
  • Substance abuse
  • Genetic factors
  • Viral infection
  • Developmental problems
  • Autoimmune disorders
  • Neurodegenerative disorders

Treatment Options for Schizophrenia

The most effective treatments for schizophrenia have an all-encompassing approach. Medications, lifestyle coaching, psychiatric care, and group therapy are all necessary aspects of treatment for this condition.

With proper treatment involving antipsychotic medications, most of the symptoms of schizophrenia can be reduced or eliminated, and episodes of active-phase schizophrenia become less frequent. Unfortunately, most of these medications come with negative side-effects, especially in the long term. Diabetes and heart complications are especially common in people taking these medications.

Treatment for Schizophrenia May Include:

  • Lifestyle coaching
  • Dietary changes
  • Addiction treatment
  • Antipsychotic medications
  • Psychiatric therapy
  • Group therapy

Medications Often Used For Schizophrenia:

  • Clozapine (Clozaril)
  • Olanzapine (Zyprexa)
  • Ziprasidone (Geodon)
  • Aripiprazole
  • Risperidone (Risperdal)
  • Quetiapine (Seroquel)
  • Haloperidol

Guide to Using CBD for Schizophrenia

Over the past decade, there’s been a growing interest in the use of CBD for treating schizophrenia.

This research started following a case report released in 1995 highlighting the improvement in a schizophrenic patient who was unresponsive to the standard antipsychotic medication haloperidol [3].

The pharmaceutical company GW Pharmaceuticals Plc recently ran a series of clinical trials on a new CBD-based drug it’s been developing called Sativex®. One of these studies explored whether or not CBD was able to relieve symptoms of schizophrenia in patients who were unresponsive to standard antipsychotic medications [2].

The GW Pharmaceuticals study was a phase 2, double-blind clinical trial conducted across 15 different hospitals in the UK, Romania, and Poland. Patients in the study were randomly put into either a treatment group (using 1000 mg per day of CBD split into two doses) or a control group (using a placebo). At the end of the six-week trial, the CBD group showed modest improvements in schizophrenic symptoms. The most substantial improvements from the study involved motor speed and executive functioning. The most significant finding in this research was that CBD didn’t appear to rely on dopamine receptor modulation — which is the primary target for current schizophrenia treatments. Instead, researchers in this study suggested the mechanism of action to be through inhibition of fatty acid amide hydrolase (FAAH), inhibition of adenosine reuptake, vanilloid receptor activation (TRPV1), and serotonin (5HT1A) receptor activation [2].

They concluded by stating that: “Because CBD acts in a way different from conventional antipsychotic medication, it may represent a new class of treatment for schizophrenia.”

More clinical trials are scheduled to explore the use of CBD for schizophrenia in larger populations and longer durations of treatment.

Results of the GW Pharmaceuticals Research Study:

(Source: McGuire et al., 2017)

Tips for Using CBD for Schizophrenia:

  1. Remember there is no cure for schizophrenia — including CBD. Treatment is designed to manage the condition, not cure it.
  2. Avoid any cannabis extracts with more than 0.3% THC — this can have a negative impact on schizophrenia over time. Stick to CBD isolates or other THC-free extracts.
  3. Use only high-quality, third-party-tested CBD products to avoid contaminated products that can worsen symptoms.
  4. Always discuss CBD or other supplement use with your doctor before taking it — some medications may have negative side-effects if mixed with CBD or other cannabinoids.

THC vs. CBD for Schizophrenia

High-THC and low-CBD extracts have been associated with a higher risk of psychotic episodes [11]. Other studies have shown that cannabis containing a high level of CBD and a level of low THC is associated with a lower risk of psychotic episodes [12].

Other studies have shown that CBD offered improvement in symptoms of schizophrenia to a similar degree as amisulpride — an antipsychotic medication [13]. CBD also had fewer side-effects.

The differences between CBD and THC and their effect on schizophrenia is very important — and likely to be the reason behind the conflicting evidence for cannabis users and schizophrenia. Some patients find relief from symptoms with cannabis use; others experience dramatically worsened symptoms after using cannabis.

If using cannabis for schizophrenia, make sure you pay attention to the THC content. Additionally, only choose products with low-THC concentrations when buying CBD.

Final Verdict: Using CBD for Schizophrenia

Schizophrenia is a highly complex neurological disorder that continues to puzzle medical researchers. However, there are several significant theories about the underlying causes of schizophrenia.

Some patients respond very well to medications; others do not.

Although CBD may improve the side-effects of the condition using several different models of schizophrenia (clinical and PCP-induced), there is also evidence that other cannabinoids — namely THC — can cause schizophrenia.

For this reason, it’s recommended that you only use CBD for schizophrenia under the close watch of a medical professional. It’s also recommended that you only use CBD products that are entirely void of THC. Additionally, research suggests that a high dose (1000 mg per day) of CBD is needed to produce even modest improvements in symptoms.


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  2. McGuire, P., Robson, P., Cubala, W. J., Vasile, D., Morrison, P. D., Barron, R., … & Wright, S. (2017). Cannabidiol (CBD) as an adjunctive therapy in schizophrenia: a multicenter randomized controlled trial. American Journal of Psychiatry, 175(3), 225-231.
  3. Zuardi, A. W., Morais, S. L., Guimaraes, F. S., & Mechoulam, R. (1995). Antipsychotic effect of cannabidiol. The Journal of clinical psychiatry.
  4. De Marchi, N., De Petrocellis, L., Orlando, P., Daniele, F., Fezza, F., & Di Marzo, V. (2003). Endocannabinoid signalling in the blood of patients with schizophrenia. Lipids in health and disease, 2(1), 5.
  5. Eggan, S. M., Hashimoto, T., & Lewis, D. A. (2008). Reduced cortical cannabinoid 1 receptor messenger RNA and protein expression in schizophrenia. Archives of general psychiatry, 65(7), 772-784.
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  8. Javitt, D. C., & Zukin, S. R. (1991). Recent advances in the phencyclidine model of schizophrenia. The American journal of psychiatry, 148(10), 1301.
  9. Spano, M. S., Fadda, P., Frau, R., Fattore, L., & Fratta, W. (2010). Cannabinoid self-administration attenuates PCP-induced schizophrenia-like symptoms in adult rats. European Neuropsychopharmacology, 20(1), 25-36.
  10. Cohen, M., Solowij, N., & Carr, V. (2008). Cannabis, cannabinoids and schizophrenia: integration of the evidence. Australian & New Zealand Journal of Psychiatry, 42(5), 357-368.
  11. Di Forti, M., Morgan, C., Dazzan, P., Pariante, C., Mondelli, V., Marques, T. R., … & Butt, A. (2009). High-potency cannabis and the risk of psychosis. The British Journal of Psychiatry, 195(6), 488-491.
  12. Schubart, C. D., Sommer, I. E., van Gastel, W. A., Goetgebuer, R. L., Kahn, R. S., & Boks, M. P. (2011). Cannabis with high cannabidiol content is associated with fewer psychotic experiences. Schizophrenia research, 130(1-3), 216-221.
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Conditions that May Respond to Cannabidiol