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Chronic marijuana use has been linked to increased risk of psychiatric problems. There’s even a name for the condition — cannabis-induced psychosis (CIP).

A new study, however, shows that a nonpsychoactive compound found in cannabis seems to reduce abnormal brain functions associated with psychosis, which includes diseases such as schizophrenia and bipolar disorder.

Researchers at King’s College London report in the journal JAMA Psychiatry that a single dose of cannabidiol (CBD) could someday be an effective alternative to the antipsychotic drugs in use since the 1950s.

These include Thorazine and Haldol, which have limited effectiveness and can cause serious side effects.

“It’s clear that the existing drugs have provided a lot of patients with schizophrenia the ability to function in society, but they’re not a cure,” Dr. Igor Grant, chair of the department of psychiatry at the University of California at San Diego School of Medicine and director of the school’s Center for Medicinal Cannabis Research, told Healthline.

“Our results have started unraveling the brain mechanisms of a new drug that works in a completely different way to traditional antipsychotics,” said lead researcher Dr. Sagnik Bhattacharyya, a reader in translational neuroscience and psychiatry at the King’s College London and the study’s lead researcher.

Grant said the study “adds to the growing hunch that CBD may be a useful alternative or adjunct to treating a very difficult to treat condition.”

A 2017 King’s College London study found participants treated with CBD had fewer psychiatric symptoms than those who received a placebo.

The research also indicated they were more likely to be evaluated as having improved conditions by their treating physician.

Grant says CBD was first revealed as a possible antipsychotic treatment by German researchers about a decade ago.

The mechanism by which it works is unclear, he says, although it’s possible CBD may inhibit an enzyme that clears anandamide. This is a natural antidepressant regulated by the brain’s cannabinoid system.

What the study revealed

The latest research compared participants receiving CBD to a placebo group as well as to a control group.

Study participants weren’t diagnosed with psychosis, but they were experiencing psychotic symptoms.

Treating people at such an early stage, before symptoms become chronic, is the best opportunity to successfully intervene with diseases like schizophrenia, Grant notes.

Researchers assigned the participants to perform a memory task involving three sections of the brain known to be associated with psychosis.

MRI scans revealed that abnormal brain activity was lower among the CBD group than among participants who received a placebo.

The findings suggest that “cannabidiol can help re-adjust brain activity to normal levels,” according to a King’s College London press statement.

“This was not a treatment trial, but it does show that CBD changes certain brain structures in a direction that indicates improvement,” Grant said.

Helping the brain ‘reset’

While big gaps remain in knowledge of the brain mechanisms involved in diseases such as schizophrenia, Grant says the King’s College London study suggests that the cannabinoid “may normalize the connectors or ‘cross talk’ in regions of the brain associated with schizophrenia.”

CBD seems to have somewhat of an opposite effect to tetrahydrocannabinol (THC), the psychoactive ingredient in cannabis. That substance is suspected of triggering psychosis in some cases.

“Although it is still unclear exactly how CBD works, it acts in a different way to antipsychotic medication, and thus could represent a new class of treatment,” said Philip McGuire, PhD, a King’s College London professor and lead author of the 2017 study.

“Moreover, CBD was not associated with significant side effects. This is also potentially important, as patients may be reluctant to take antipsychotic medication because of concerns about side effects,” he said.

A possible preventive tool

Bhattacharyya and his colleagues are currently undertaking a large-scale study to determine whether CBD can be used to prevent young people at risk of psychosis from developing mental health disorders.

“There is an urgent need for a safe treatment for young people at risk of psychosis,” Bhattacharyya said. “One of the main advantages of cannabidiol is that it is safe and seems to be very well-tolerated, making it in some ways an ideal treatment. If successful, this trial will provide definitive proof of cannabidiol’s role as an antipsychotic treatment and pave the way for use in the clinic.”

In the United States, 31 states and the District of Columbia — but not the federal government — have decriminalized or legalized marijuana for medical use.

Smoking or ingesting marijuana delivers a dose of both CBD and THC.

However, compounds containing only CBD are also offered for sale in many states where medical marijuana use has been legalized.

The U.S. Food and Drug Administration (FDA) has also approved two cannabis-derived medications for sale and use, including a CBD-based liquid medication called Epidiolex that’s used to treat two types of childhood epilepsy.

Other cannabinoids, such as dronabinol and nabilone, have been approved to treat cancer-related side effects such as nausea.

Cannabis contains more than 150 cannabinoids. Many may have potential for therapeutic use, says Grant.

“It’s not the case that CBD is good and THC is bad,” Grant noted. “It really depends on what you’re trying to do.”