Ironically, Scientologists declare that they are "of sound mind" when they sign this contract agreeing to commit to the group's "Sea Organization" for the next one billion years.
According to this new article in the New Yorker, they also do stuff like this:
[David] Miscavige [the group's leader] announced that everyone was going to play musical chairs. Only the last person standing would be allowed to stay on the base. He declared that people whose spouses “were not participants would have their marriages terminated.” The St. Petersburg Times noted that Miscavige played Queen’s “Bohemian Rhapsody” on a boom box as the church leaders fought over the chairs, punching each other and, in one case, ripping a chair apart.
A Scientology spokesperson confirmed that "a musical-chairs episode" did take place at the group's "Gold Base" in the desert, but denied the remainder of the allegations.
The New Yorker's article is definitely worth a read, and provides links to more leaked Scientology documents as well as pleadings filed in cases brought against the group by former members. Good stuff.