No doubt most people know what an advance directive is regarding end-of-life decisions, but are probably unaware that those afflicted by mental illness can provide an advance directive for their care in the event that they are incapacitated by an acute exacerbation of their illness.
Psychiatric advance directives (PADs) are relatively new. They are legal documents which spell out the consumer’s preferences for treatment in the event that they become incapacitated or unable to give or withhold informed consent for treatment. 
These documents authorize a specified person or persons to act as a surrogate in making decisions about care and treatment. They provide a Durable Power of Attorney for Healthcare which specifies the consumer’s wishes regarding their mental health treatment. The document can limit the agent’s authority to specific types of decisions.
California law does not allow the agent to consent to commitment or placement in a mental health treatment facility. Nor can the agent consent to psychosurgery, sterilization, abortion, or electroconvulsive treatment (ECT). The agent may however, make other decisions based on what s/he feels the consumer would do if s/he was competent.
Almost all states have some process regarding a psychiatric advanced directive, but there can be many variations to the process. In California, the psychiatric advanced directive allows the consumer to appoint a proxy or agent to make decisions on their behalf, and it also allows the consumer to state specific about their care including medications and hospitalizations with or without appointing a proxy.
In California it is not necessary for a court to determine the consumer is not competent to make decisions before an agent or the PAD is invoked. In fact, the consumer can specify in the PAD that s/he wishes the directives be followed at all times regardless of whether s/he is not competent to make decisions.
Of importance is the fact that even though the consumer can specify that they don’t want to be given medications or hospitalized, state law can supersede this in the event of a psychiatric emergency and require hospitalization for the consumer’s safety or the safety of others.
The PAD remains valid until the consumer revokes it, or until any expiry date specified in the document.
Resources:
National Resource Center on Psychiatric Advance Directives