He was educated first in London and later in Belper, Derbyshire. In 1947, he became a medical student at Caius College, Cambridge, gaining a First Class Honours degree in the Part 2 Tripos in Psychology. He completed his clinical studies in Bristol and, when in the Royal Air Force, gained a knowledge of electroencephalography. He spent two years at Oxford, and for his research received the M.D. (Cambridge) in 1959.
He became a lecturer in the Department of Psychological Medicine of Edinburgh University in 1959. In 1963 he was awarded the Gaskell Gold Medal in Clinical Psychiatry of the Royal Medico-Psychological Association, and in the same year the degree of D.Sc. of Edinburgh University. In 1965-1967, on leave from Edinburgh, he established a Department of Psychiatry in the University of Western Australia. He became a Foundation Fellow of the Royal College of Psychiatrists in 1971, and in 1977 was appointed to a personal Chair in Edinburgh University.
In the 1980s in research with Kirstine Adam, he reported that the sleeping drug triazolam (Halcion), when taken nightly caused adverse mental effects by day. This led on to 1991 when triazolam was banned in the United Kingdom because, as the Committee on Safety of Medicines said after studying further unpublished research by the Upjohn Company of Kalamazoo (Halcion's manufacturers), "triazolam causes frequent and disabling psychiatric adverse reactions at doses of 0.5 and 1mg when used in a population of young and middle-aged patients with no mental illness". (The Daily Telegraph. October 2, 1991). In 1992, the Upjohn Company of Kalamazoo, the makers of Halcion, sued him in London for libel and he countersued in a 62-day trial.
He married fellow sleep researcher, Dr Kirstine Adam, and had four children from his late wife. His son is Andrew Oswald, Professor of Economics.
- Phil Davison. "Prof Ian Oswald". Herald Scotland. Retrieved 2012-05-25.
- Adam, Kirstine; I. Oswald (1989). "Can a rapidly-eliminated hypnotic cause daytime anxiety". Pharmacopsychiatry 22: 115–119. doi:10.1055/s-2007-1014592. PMID 2748714.
- Hooper, David (2000). Reputations under Fire. Winners and Losers in the Libel Business. Little, Brown and Company. ISBN 0-316-64833-7.