An ingredient in cannabis called cannabidiol or CBD has shown promise in a clinical trial as a potential new treatment for psychosis, scientists said Friday.

In research involving 88 people with psychosis, a mental disorder characterized by anxiety, paranoia and hallucinations, the scientists found patients treated with CBD had lower levels of psychotic symptoms than those who received a placebo.

They were also more likely to be rated as improved by their psychiatrist, the study found, and there were signs of better cognitive performance and functioning.

The main psychoactive ingredient in cannabis is delta-9-tetrahydrocannabinol, or THC. It can induce paranoia and anxiety and other unpleasant psychotic symptoms.

Two ingredients, two effects

But its second major constituent, CBD, has the opposite effects to THC, leading scientists to think it might one day be useful as a treatment in mental health.

Scientists at King’s College London’s Institute of Psychiatry, Psychology & Neuroscience conducted a placebo-controlled trial of CBD in patients with psychosis and published their findings in the American Journal of Psychiatry.

Small trial

In the trial, 88 patients with psychosis received either CBD or placebo for six weeks, alongside their existing antipsychotic medication. Beforehand and afterwards, the scientists assessed symptoms, functioning and cognitive performance, and the patients’ psychiatrists rated their overall condition overall.

“The study indicated that CBD may be effective in psychosis: patients treated with CBD showed a significant reduction in symptoms, and their treating psychiatrists rated them as having improved overall,” said Philip McGuire, who co-led the trial.

He noted that trial patients also reported few adverse side effects, and added: “Although it is still unclear exactly how CBD works, it acts in a different way to antipsychotic medication, and … could represent a new class of treatment.”