There are many, many studies linking cannabis use to schizophrenia and psychosis – including one recently that suggests it is the latter (or at least a latent predisposition towards the latter) that influences the former rather than vice versa.

Now, research reveals there is a naturally occurring component within cannabis that can actually help suppress symptoms of psychosis, at least in the short-term. The study has been published in JAMA Psychiatry. 

The substance in question is cannabidiol (CBD), and one dose may be all it takes to alleviate certain brain abnormalities, including delusions and hallucinations. It is the very same cannabinoid that has been purified and licensed by the FDA as a treatment for rare and severe forms of epilepsy. 

To study its effects on psychosis, scientists from King's College London (KCL) recruited 33 young people who had been experiencing distressing psychotic symptoms but were not yet diagnosed with psychosis and a further 19 to act as controls. Sixteen of the at-risk group were offered a single dose of cannabidiol (600 mg). Everyone else took a placebo.

Three hours later, volunteers performed a memory task while their brain was being scanned by an MRI machine. The task had been specifically designed to engage three parts of the brain connected to psychosis, including activities such as saying whether or not a pair of words went well together, then recalling which word had been paired with which.

The 33 young people with psychosis-like symptoms continued to show higher levels of abnormal brain activity in these brain regions than the control group (unsurprising), but those who had taken the cannabidiol supplement showed lower levels than those who had taken the placebo.

It's not the first time research at KCL has shown that cannabidiol may work as an adversary to tetrahydrocannabinol (THC), the substance responsible for your high (in recreational cannabis, levels of cannabidiol are too low to have much of an antipsychotic effect). And if the results are replicated, it may show that cannabidiol extract could be used to help to stamp out abnormal brain activity, at least partially.

Right now, the World Health Organization estimates that roughly 100,000 young people experience some form of psychosis every single year and up to three people in every 100 will go through a psychotic episode at some point during their lifetime. The scientists involved hope this research will one day be used to treat those with psychosis untreatable by other means. 

"The mainstay of current treatment for people with psychosis are drugs that were first discovered in the 1950s and unfortunately do not work for everyone," Sagnik Bhattacharyya from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at KCL said in a statement. "Our results have started unravelling the brain mechanisms of a new drug that works in a completely different way to traditional anti-psychotics."

Next up: Bhattacharyya and his team at the IoPPN are working on a large-scale trial to examine whether or not it can be prescribed to young people at a high risk of psychosis to manage their symptoms. This will be the first of its kind.

"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," Bhattacharyya added. "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."