While the etiology and course of homelessness is very complex, the literature review revealed a general path in the person's life of early abuse or victimization, followed by increasing alcohol and other drug use, followed by increasing homelessness. Homelessness is ubiquitous across California, touching all metro and rural areas and including all walks of life irrespective of race, age, gender, and household status. Census data from 1990 show that an estimated 50,000-100,000 people in California are homeless on any given day. The definitions and degrees of homelessness vary across databases and regions of the State.
Homeless people suffer from a very high prevalence of substance disorders.
The homeless are beset by a higher prevalence of personal disabilities than the housed population. Homeless adults are 2-12 times more likely to suffer a serious and disabling mental illness and significantly more likely to suffer from common and serious physical health problems than housed adults.