Sigmund Freud, the creator of psychoanalysis, was one of the first doctors to research and write about the unconscious mind and repressed memories. Freud believed that psychological problems could manifest as physical symptoms.
Freud, an Austrian neurologist, had a significant impact on both psychology and popular culture, introducing terms such as "Freudian slip" into everyday usage. While many of his theories have generated controversy, Freud continues to be known as one of the leading thinkers of the 20th century, notes About.com.
With the help of his follower Princess Marie Bonaparte, Freud, his wife and daughter fled the Nazis to the safety of Paris in 1938. In 1939, Freud died in London from a fatal dose of morphine that he requested from his doctor as he fought terminal cancer in his jaw.