Hallucination-inducing "magic" mushrooms could help some people blunt the anxiety caused by chronic depression, according to a small-scale study released on Tuesday.

"This is the first time that psilocybin" - a mind-altering chemical in several species of mushroom - "has been investigated as a potential treatment for major depression," lead author Robin Carhart-Harris of Imperial College London said.

The study only involved 12 people and did not use a placebo-taking control group.