Here’s EWTN’s take on hypnotism. Bill Bilton appears to be a forum moderator:
Hypnotism
Question from on 08-23-2002:
What is our church’s opinion of hypnotism?
Answer by Bill Bilton on 08-27-2002:
According to Catholic principles, hypnotism is not wrong in itself, so its use under certain circumstances is permissible. But since it deprives the subject of the full use of reason and free will, a justifying cause in ncessary for allowing it to be practiced. Moreover, because hypnotism puts the subject’s will in the power of the hypnotist, certain precautions are necessary to safeguard the subject’s virtue, and to protect him or her against the danger of being guilty of any injurious actions.