Is SF atypical in the number of mentally unstable homeless people? I moved to the US a year ago and am still blown away by the shear number of drugged up or cra

Is SF atypical in the number of mentally unstable homeless people? I moved to the US a year ago and am still blown away by the shear number of drugged up or crazy people living in the middle of the city. I've seen plenty of homeless people on my travels around the world but usually they are poor, not mentally unstable (to my knowledge).