An advanced directive, also called a living will, is a legal document that gives instructions to doctors. It takes effect when it has been medically determined that an individual is either physically or mentally incapacitated beyond the ability to express his or her wishes in terms of medical treatment. Typically, it's used when a patient is in a vegetative state and needs life support to be kept alive. An advanced medical directive lets health care providers know what sorts of treatments and medications are approved by the patient.
The most important advantage of an advanced directive is it allows a person to express choices and wishes to health-care providers. This strongly asserts the patient's choice into what treatments or procedures will be used in an emergency. It provides peace of mind because it answers the matter of whether life support should be used.
Another benefit of an advanced directive is that it can prevent unnecessary delay in administering medical treatments that require consent. Without an explicit statement, precious time could be lost determining who has the legal authority to act on behalf of a critical patient. Medical options might be lost with the passage of mere minutes.
To make informed decisions on a living will requires some research into exactly what sort of medications and treatments should be administered in an emergency. Thus, one of the collateral benefits of preparing an advanced directive is that it gets people thinking about their opinion on life support and can get them talking to their doctors about exactly what specific procedures entail.
The major drawback to an advanced directive is that it is a piece of paper. A doctor might not know of its existence or it might not be produced in time to be of much use. There's also a possibility it won't be honored if it's from another state. Some states explicitly overrule living wills if the patient is a pregnant.
Finally, some people fear that an advanced directive interferes with adequate care. In one sense, the directive cannot contemplate every possibility, which is why it's usually suggested that a health-care proxy also be designated and make actual decisions with the benefit of knowing the facts. Furthermore, it's feared that if a doctor knows a patient does not want to be kept alive on artificial life support at all costs, then other measures might not be taken either.