Physicians make at least an informal decision on a continual basis regarding the patient's ability to give informed consent. The difference between competency and capacity is a common misconception, and the terms, competency and capacity, are often used interchangeably in consult requests. Capacity is often considered an all-or-none phenomenon, and this may be the most common fallacy. The most common diagnoses which prompt request for capacity evaluation include dementia and delirium. Other diagnoses include substance abuse, affective disorders, personality factors, and psychotic disorders. Some states have laws which limit the ability to give consent to medical treatment for certain groups of patients. For instance, patients who are involuntarily committed for mental illness in Louisiana may not give consent for major surgery without a court order. Denial, a defense mechanism utilized to avoid unpleasant effects by denying aspects of reality, can be helpful for patients in some cases.