|Style over substance|
Primal scream therapy, or simply primal therapy, was an odd bit of woo popularized by Arthur Janov in his 1970 book, The Primal Scream. His hypothesis was that psychological problems are caused by early childhood trauma, such as during birth. These traumatic incidents could be re-experienced and then emotionally discharged by expressing them during therapy by screaming. John Lennon, Yoko Ono and Steve Jobs were brief adherents of the movement.
Although Janov was then a respected psychologist and did not (as far as is known) derive his hypothesis from superficially similar ideas which were already then regarded as quackery, although his focus is somewhat similar to the Dianetics (Scientology) notion of removing "engrams" by re-experiencing traumatic incidents and emotionally discharging them, and to the quack therapy of re-experiencing birth traumas through rebirthing. No empirical studies ever found the therapy useful or sound, however, and nothing eventually came of his hypothesis except yet another quack movement. Today Primal Therapy is lumped in with other fringe therapies which emerged as part of the Human Potential Movement.
Having said all that, Screamadelica by the band Primal Scream is a fantastic album. Tears For Fears named themselves after an idea in primal scream therapy and are likewise a fantastic band. Lennon's album John Lennon/Plastic Ono Band, recorded while he was an adherent of the movement, is often regarded as his finest solo album.
 More claims
These are all quotes from The Primal Scream by Arthur Janov, Perigree 1981 softcover edition.
 Primal therapy makes your boobies grow
"Perhaps the most dramatic changes which take place in post-Primal patients are physical… For example, about one-third of the moderately flat-chested women independently reported that their breasts grew" (p. 154)
 Primal therapy makes everything else grow
"Two male patients in their early twenties told of beard growth for the first time in their lives. Several others reported giving off an odor for the first time after perspiring. Several patients noted growth of hands and feet." (p. 154)
"There are neurotic symptoms which are not usually thought of as such—being short, for example… We see that the patient has grown and thus may infer that his being short was indeed a symptom—his idiosyncratic resolution of the inner contradictions which plagued him." (p. 134)
 Primal therapy screams away the gay
"I do not believe that there is a basic genetic homosexual tendency in man. If this were true, the cured patient would still have his homosexual needs, which he does not. Post-Primal patients who have been latent and overt homosexuals before report no homosexual leanings, fantasies, or dreams." (p. 308)
 In case I missed anything
"I could go on endlessly listing all the symptoms which Primal Therapy has eliminated, from menstrual cramps to asthma. But that would tend to make Primal Therapy seem some kind of panacea and thus lessen its credibility." (p. 134)