Karin Stephen was born in 1890. She was a fellow of Newnham College, Cambridge and married Adrian Stephen (brother of Virginia Woolf and Vanessa Bell) just before the First World War; as conscientious objectors, they spent the war working on a dairy farm. After the war, they both became interested in training as psychoanalysts. In order to qualify, they trained as doctors and went into analysis with James Glover until his untimely death in 1926, when Karin went to Sylvia Payne and Adrian to Ella Sharpe. They were accepted as associate members of the British Psychoanalytical Society in 1927; Adrian became a full member in 1930 and Karin in 1931.

Karin entered private practice as a psychoanalyst. She gave the first course of lectures on psychoanalysis ever given at Cambridge University; these were highly successful and formed the basis of a book for medical students. She was active on the Public Lectures Committee of the British Psychoanalytical Society but was sometimes critical of the society and contributed to the Extraordinary Business Meetings held during the Controversial Discussions.

During the Second World War, her husband, angered by anti-semitism, abandoned his pacifist stance and joined the Royal Army Medical Corps as an army psychiatrist. Karin became a driver in the Queen�s Messenger Flying Squad Food Convoy.

Karin Stephen suffered from increasingly severe deafness and from manic-depression; following the death of Adrian Stephen in 1948, her health deteriorated and she committed suicide in 1953.