Psychiatrists and clinical psychologists are often asked to evaluate a patient's capacity for making life-and-death decisions at the end of life. Persons with a psychiatric condition such as delirium or clinical depression may lack capacity to make end-of-life decisions. For these persons, a request to refuse treatment may be taken in the context of their condition. Unless there is a clear advance directive to the contrary, persons lacking mental capacity are treated according to their best interests. This will involve an assessment involving people who know the person best to what decisions the person would have made had they not lost capacity. Persons with the mental capacity to make end-of-life decisions may refuse treatment with the understanding that it may shorten their life. Psychiatrists and psychologists may be involved to support decision making.