Due to the necessity of hiding as a Jew during the Second World War, De Wied only started in 1947 studying medicine at the University of Groningen. In 1952 he received his PhD with his thesis "Vitamin C, Adrenal gland and Adaptation" and in 1955 he graduated as physician. In 1961 he was appointed professor of experimental endocrinology and from 1963 he served as director of the Rudolf Magnus Institute and professor of pharmacology in Utrecht.
De Wied gained international esteem chiefly by his discovery of neuropeptides and their value to memory and learning. The subject was made comprehensible to the public when the media coined the term "learning-pill" describing the effect of the discovery.