French psychiatrist. He is known for his detailed work on neurosis. His early work focused on the psychasthenias, a term he coined to describe anxiety, phobias, and obsessional disorders. He went on to formulate a comprehensive theory of development, in which abnormal behaviour and neuroses were seen to result from an individual's failure to fully integrate psychological functions associated with a given developmental stage.
It was as a student of Jean-Martin Charcot that Janet first became interested in the study of neurosis and its treatment by hypnosis. From 1895 he was director of studies in experimental psychology at the Sorbonne before being appointed professor of experimental and comparative psychology at the Collège de France 1902, a post he held until 1936. His major works, as yet not fully translated into English, include Névroses et idées fixes 1898, Les Obsessions et la psychasthenie 1903, and Les Névroses 1905.