Catherine Elizabeth "Karin" Stephen, née Costelloe, was the daughter of Benjamin Francis Conn Costelloe, an Irish lawyer, and his American-born wife Mary Smith, who abandoned her first husband and two children to live with Bernard Berenson in Italy. Karin and her sister Rachel (later Ray Strachey) were brought up by their maternal aunt, Alys Pearsall Smith (first wife of Bertrand Russell). Karin attended Cambridge University, where she became a Fellow of Newnham College. In 1914, she married Adrian Stephen, a brother of Virginia Woolf and Vanessa Bell; as conscientious objectors, they spent the years of World War I working on a dairy farm in Essex. After the war, the couple trained as doctors and then went into analysis. She wrote a chapter called The Misuse of Mind: A Study of Bergson's Attack on Intellectualism, published in The Philosophical Review in 1922. She became a full member of the British Psychoanalytical Society in 1931 and went into private practice as a psychoanalyst. She gave the first lecture course on psychoanalysis ever given to medical students at Cambridge University. Her course of six lectures was given for several years, and formed the basis of her classic textbook The Wish to Fall Ill: A Study of Psychoanalysis and Medicine (1933). During World War II, she served as a driver in the Queen’s Messenger Flying Squad Food Convoy. She suffered from increasingly severe deafness and manic depression and committed suicide in 1953.