[quinnchr]

Actually, only 35% of San Francisco's homeless population has some sort of Psychiatric condition. According to a survey of SF's homeless the biggest barriers to finding work (as of 2015) were:

  28% said no permanent address
  20% said alcohol or drug use
  17% said disability
  14% said age
  13% said need for clothing/shower facilities
  ...
  9% said mental health concerns

So it does seems like lack of housing is the largest barrier for SF's homeless population. Additionally, mental illness is most prevalent amongst the chronically homeless, which only make up about 25% of the homeless population in SF. The vast majority of homeless people are homeless for months not years, and the many programs to aid them in finding housing and preventing homelessness in the first place have a significant measurable effect on the average number of homeless shelter entries and length of stay.

Source: https://sfgov.org/lhcb/sites/default/files/2015%20San%20Fran...

[twblalock]

Asking mentally ill people if they are mentally ill is not a reliable way to determine if they are mentally ill. The same is true for alcoholics and drug addicts.

Many people will deny their circumstances because they are mentally ill and don't realize it, or are simply in denial, or because they think they will get more help if they hide their problems.

[quinnchr]

Yes this is true of any mental health issue in any population, we can only rely on self-reporting. If you have any sources that show "almost all" homeless people in SF are mentally ill, I'd be interested to read them.

From what I've read, at the national level the incidence of serious mental illness in the homeless population are around 20 - 25%. So the numbers for San Francisco seem reasonable.