Goodreads Question on The Clown Forest Murders

I recently posted on Goodreads a trivia question about The Clown Forest Murders.  The reader is asked to answer how many characters have mental problems.  I believe the choices ranged up to seven characters.  The key is, of course, to define what is meant by "mental problems," with different answers if you require a diagnosis or consultation with a professional or are willing to accept your own diagnosis based on behavior.  I expect I'll elaborate in a blog to come.