Here are some jokes I found when searching. I thought they were pretty funny.
How do you tell the difference between the staff and the inmates at a psychiatric hospital?
The patients get better and leave.
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What happens when a psychiatrist and a hooker spend the night together?
In the morning each of them says: "120 dollars, please."
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If someone with multiple personalities threatens to kill herself, is it considered a hostage situation?
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How many psychologists does it take to change a light bulb?
-Just one, but the light has to really want to change.
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I may be schizophrenic, but at least I have each other!
Here is a link to several other jokes, I hope it's ok that I included that.
http://www.mentaljokes.com/