[1] He was born as the eldest son of district physician Stian Erichsen (1867–1953) and his wife Magdalene Susanne Werner (1870–1967).
[2] After a failed examen artium in 1919 he decided to make a journalistic career, and was employed as a night assistant by the Morgenbladet newspaper.
In the 1920s, Erichsen worked as a journalist in the Parliament of Norway, notably covering the impeachment case against former Prime Minister Abraham Berge in 1926 and 1927.
Following Gjerløw's imprisonment during the Second World War, Erichsen became alone responsible for Morgenbladet's enterprise; he was its managing director from 1939 to 1947 and its editor-in-chief from 1941 to 1943.
[1] Before becoming managing director of the Norwegian News Agency in 1961, he penned three books on the press history of Norway.