Doubts on cannabis benefits

There is inadequate evidence that cannabinoids relieve depression, anxiety disorders or attention-deficit hyperactivity disorder, scientists have said.

The meta-analysis also looked at the impact of medicinal cannabinoids on Tourette's syndrome, posttraumatic stress disorder and psychosis.

Research which combined 83 studies involving 3,000 people suggested their use for the six mental health conditions cannot be justified based on the current evidence.

Scientists said this is due to a lack of evidence for their effectiveness, and because of the known risks of cannabinoids.

But the study, published in the Lancet Psychiatry journal, suggests there is very low quality evidence that pharmaceutical tetrahydrocannabinol (THC) may lead to a small improvement in symptoms of anxiety in individuals with other medical conditions.

Lead author Professor Louisa Degenhardt, of the National Drug and Alcohol Research Centre (NDARC) at UNSW Sydney, Australia, said: "Our findings have important implications in countries where cannabis and cannabinoids are being made available for medical use.

"There is a notable absence of high-quality evidence to properly assess the effectiveness and safety of medicinal cannabinoids compared with placebo, and until evidence from randomised controlled trials is available, clinical guidelines cannot be drawn up around their use in mental health disorders."

Medicinal cannabinoids include medicinal cannabis.