Chris and Xand continue their conversation with Dr James Rucker, a consultant psychiatrist at King's College London who is leading the European arm of a global trial of a psychedelic designed to treat people with severe depression.

They discuss the history of psychedelics, the discovery of LSD and the popular (and often illegal) practice of microdosing. Is there any evidence to suggest that taking minute quantities of psychedelic substances will boost your brain function or mood?

Chris and Xand also discuss their own experience of taking psychedelics several years ago for a TV series about traditional medicines.

If you’d like to share your thoughts on this or any other topic covered on the podcast, you email us at whatsupdocs@bbc.co.uk or Whatsapp on 08000 665 123.

Presenters: Drs Chris and Xand van Tulleken Guest: Professor Andy Smith Producer: Jo Rowntree Executive Producer: Rami Tzabar Editor: Kirsten Lass Assistant Producer: Maia Miller-Lewis Assistant Producer and Researcher: Emily Bird Tech Lead: Reuben Huxtable Social Media: Leon Gower Digital Lead: Richard Berry Composer: Phoebe McFarlane Sound Design: Melvin Rickarby At the BBC: Assistant Commissioner: Greg Smith Commissioning Editor: Rhian Roberts

A Loftus Media production for BBC Radio 4.