Did Ronald Reagan's LPS Act increase homelessness in California?

Question

I have heard and read claims suggesting that California passed a law when Ronald Reagan was governor that lead to a surge of homelessness and that explains to a large extent the relative high rate of homelessness (1) in the state.

Here are some examples of sources that echo and discuss such claims: (2) and (3). As context to the question, below are two quotes from "A New Vision for Mental Health Treatment Laws: A Report by the LPS (Lanterman–Petris–Short) Reform Task Force" (4):

Quote 1:

Reagan's role, besides signing the bill, was using it as a reason to cut his budget. What Reagan did was, at the same time the bill was passed, to reduce the budget for state mental hospitals. His budget bill "abolished 1700 hospital staff positions and closed several of the state-operated aftercare facilities. Reagan promised to eliminate even more hospitals if the patient population continued to decline. Year-end population counts for the state hospitals had been declining by approximately 2000 people per year since 1960."

Quote 2:

Frank Lanterman would say days before his death, "I wanted the LPS Act to help the mentally ill. I never meant for it to prevent those who need care from receiving it. The law must be changed".

1. Is there any evidence (besides the quoted report) supporting these claims?
2. To what extent can the relative high rate of homelessness in California (1) be attributed to the signing of this act?

Answer 1

Ronald Reagan did sign a law in 1967, namely the Lanterman–Petris–Short Act, which reduced the ability of the state to institutionalise mentally ill people involuntarily. It had the causal consequence of increasing the number living on the streets.

It was not Reagan's proposal, so it is difficult to blame him for this law; since it was seen as increasing the civil rights of mentally ill people, it is difficult to blame him for not vetoing it.

A bigger question is whether there was sufficient out-patient care and hostel housing provided to meet the resulting demand. But even if there had been, there would probably have been an increase in homelessness.