I worked for 20 years in crisis public mental health -mostly in a short term 14 to 30 days. In the last nine years of that work I saw more homeless mentally ill with drug addiction problems. They revolved through the program and back to the streets. All the 3 or 4 main homeless facilities were constantly full. That was 7 years ago. Judging by the increase of homeless encampments I can only assume the problem is much worse.

Yes the study is skewed because it does not address the crux of the problem which is complex. Having to do with massive economically inequality, single parent homes, poor parenting, massive influx of drugs to poor neighborhoods, use of drugs having triggered underlying mental illness and/or exacerbating existing mental illness and on and on...