It's not that other forms of psychotherapy are scientifically shown to be 0% effective; it's just that evidence-based psychotherapy is a surprisingly recent field. Psychotherapy can still work even if some fields of it have not had rigorous studies showing their effectiveness... but you might as well go with a therapist that has training in a field of psychotherapy that has some scientific method behind it.
http://www.mentalhelp.net/poc/view_doc.php?type=doc&id=13023&cn=5
To whom it may concern:
This thread is for the discussion of Less Wrong topics that have not appeared in recent posts. If a discussion gets unwieldy, celebrate by turning it into a top-level post.
(After the critical success of part II, and the strong box office sales of part III in spite of mixed reviews, will part IV finally see the June Open Thread jump the shark?)