Magic mushrooms 'promising' in depression

BBC article on a report in the Lancet.

A hallucinogenic chemical in magic mushrooms shows promise for people with untreatable depression, a short study on just 12 people hints.

Eight patients were no longer depressed after the "mystical and spiritual" experience induced by the drug.

The findings, in the Lancet Psychiatry, showed five of the patients were still depression-free after three months.

Experts cautiously welcomed the findings as "promising, but not completely compelling".
As well as the main topic, it also raises the issue of the difficulties in even being able to conduct such research.
I don't think there is much doubt that people's perceptions of an experience can have a transformative effect, regardless of the underlying mechanism. Also the drug may interact with the person's neuro-receptors in a manner that helps depression in a way that is also separate from the underlying reality of the experience.

In short, the mere psychological benefit of the experiences produced by these drugs seems consistent with both brain based and non brain based hypotheses. Or am I missing something here?