After holding various positions during the 1940s, Clausen joined the National Institute of Mental Health in 1948 as a research consultant.
[3][4] Throughout World War II, Clausen performed research on the morale of Army soldiers during combat.
[5][6] After working for a year in research design for the Veterans Health Administration in Washington, D.C., Clausen taught sociology from 1946 to 1948 at Cornell as an assistant professor.
[8] In the early 1960s, Clausen expanded his schizophrenia research when he studied how mental illness effected marriages.
[9] In 1960, Clausen joined the University of California, Berkeley as a sociology professor and the director of the human development department.
[4] Clausen published the Berkeley longitudinal study findings in a 1993 book titled American Lives: Looking Back at the Children of the Great Depression.
[11] Apart from writing, Clausen was an editor for Socialization and Society in 1968 and the 1982 publication of Present and Past in Middle Life.