Primal therapy became very influential during a brief period in the early 1970s, after the publication of Janov's first book, The Primal Scream. It inspired hundreds of spin-off clinics worldwide and served as an inspiration for many popular cultural icons. Singer-songwriter John Lennon, actor James Earl Jones, and pianist Roger Williams were prominent advocates of primal therapy.[2] Primal therapy has since declined in popularity, partly because Janov had not demonstrated in research the outcomes necessary to convince research-oriented psychotherapists of its effectiveness.