Advocates for homeless people are leery of casting too much blame for the state’s crisis on mental health and substance abuse issues. They argue that plenty of low-income residents in other states struggle with drug addiction and debilitating psychological conditions. They simply manage to remain off the streets because the rent is cheaper.

But recent data suggests these issues are more prevalent among people experiencing homelessness than previously reported, especially for those living on the street. About half of the unsheltered nationally report that mental health and/or substance abuse contributed to their loss of housing. A Los Angeles Times investigation found two-thirds of L.A. County’s residents living on the streets suffer from a psychological or substance abuse disorder, far more than what’s been reported in official statistics that exclude mental disorders that aren’t “long-term.”

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Methamphetamine use is up across the West Coast, and is often to blame for some of the most visible episodes of homelessness seen on California streets. Unfortunately, physicians say meth addiction is confoundingly difficult to treat. While methadone is available to wean heroin addicts off of opioids, no such replacement medication exists for meth.

Worse still, meth can exacerbate existing mental illnesses. Addiction and psychological conditions are often inextricably intertwined, and present a complex case for outreach workers or (more often) law enforcement to confront. A disconcerting number of California board-and-care facilities, which have traditionally housed low-income patients with schizophrenia and other severe conditions, have shuttered in recent years.

Many have also blamed California’s conservatorship laws for making it too difficult to compel treatment for people with mental illness or drug addiction living on the street. Civil libertarians and disability rights groups argue that conservatorship —when a court-appointed official manages another person’s life, including medical decisions — should be used as sparingly as possible, as it risks violating civil liberties and is a hollow remedy given the severe shortage of actual treatment options. Under a 1967 state law known as the Lanterman-Petris-Short Act, Californians can be held for treatment against their will only if they are deemed a danger to themselves or others, or are determined to be gravely disabled. Other states such as New York do not impose such strict requirements. California is experimenting with allowing three counties to take legal power over mentally ill people living on the street, but only in limited circumstances.

Finally there is the eternal question of cause and effect: The severe stresses people face when they lose shelter and are forced to live exposed on the streets can also wreak havoc on their mental health and lead to substance abuse.