After the war, Osmond joined the psychiatric unit at St George's Hospital, London where he rose to become senior registrar. His time at the hospital was to prove pivotal in three respects: firstly it was where he met his wife Amy "Jane" Roffey who was working there as a nurse, secondly he met Dr John Smythies who was to become one of his major collaborators, and thirdly he first encountered the drugs that would become associated with his name (and his with theirs): LSD and mescaline. While researching the drugs at St George's, Osmond noticed that they produced similar effects to schizophrenia and he became convinced that the disease was caused by a chemical imbalance in the brain. These ideas were not well received amongst the psychiatric community in London at the time. In 1951, Osmond and Smythies moved to Saskatchewan, Canada to join the staff of the Weyburn Mental Hospital in the southeastern city of Weyburn, Saskatchewan.