Original sentence: He has done research on the health effects of cannibis, cocaine, and other recreational drugs.John Henry is a professor specializing in toxicology in the Faculty of Medicine, Imperial College London, at St Mary's Hospital
Edited sentence: Independent article.Professor  John Henry, an expert on the effects of drugs, says that ecstasy is a relatively safe drug to take from an acute point of view, but warns that every time someone takes the drug the serotonin terminals in their brain are irreparably damaged