One big caveat? No guns of any kind—stun or otherwise—are allowed in space. This means the crew is largely dependent on their own strength to control an unmanageable astronaut. Once restrained, the astronaut can be administered tranquilizers or anti-depression, anti-anxiety, and antipsychotic medication depending on their condition. Should they not voluntarily take these medicines, the drugs could be forcibly administered with a shot to the arm.
Luckily, according to NASA spokesman James Hartsfield, "No NASA astronaut at the space station has been treated in orbit with antipsychotic or anti-depression medication, and no NASA shuttle crew member has required antipsychotic medications."
NASA requires their astronauts to see a psychologist every two weeks, meaning disorders could be detected quickly, but what about space tourism? When we start sending untrained millionaires into space, shuffling them into tiny quarters and deep isolation, you have to think it's only a matter of time before something goes wrong.