Paranoia and compulsive thought robs a person of creativity. The mind is laser focused on terrible scenarios that are borderline fantasy. You make up stories about the people around you conspiring against you, you invent worlds of terrible insects and viruses. Your mind is so consumed by all that, that you don't have a chance to write something truly creative. You also work hard to appease your obsessions, just so you can sleep.
I know because I have bipolar disorder and some OCD. Last night, I was obsessed with eliminating bedbugs and making sure my car was locked. I could have been writing fiction instead, and using all that obsessive thought on something fun. I think some people aren't consciously aware of this, or can't make themselves focus on other things that matter. I got swept up in mine, but I was able to catch myself doing it. I realized it's better to put the obsession to work inventing fantasy worlds.
I meet homeless people all the time who work hard to invent elaborate stories about how much they are suffering in their life. Many have a rehearsed "poverty speech."
It starts out believable, but goes to a point where they are inventing medical problems that science has yet to discover. A woman once told me that her stomach had been surgically removed. Another woman (not homeless, but acted like it) thought the question of how many times you swallow in a minute was a life or death issue. Other homeless people tell you they play checkers with Obama.
One man I met tends to fabricate people in the neighborhood that he knows, and their relationship to him. He will point to someone and tell me a story about them, but the person he mentions does not show any sign of recognition. If he is that well known, why is he asking me for help?
Just think if an ounce of that creativity got redirected to the writing of plays or music. Or creating a "mind palace".
There is a line in the Neverending Story novel that basically says that lies exist because people stopped using their imagination.
It's not just the homeless. People with houses sometimes come up with elaborate fantasies about how people of other races are talking behind their back and conspiring against them. Or planning a robbery. And they spend huge amounts of time and money on home security.
In summary, your mind is a ship. If you are aware of the steering wheel, think about where you want to go and who you want to be, or you won't like where you end up.