Family members, other important people in the patient's life, and records of prior medical and psychiatric treatment are frequently useful sources of information. Collateral information is particularly important when patients have impaired insight, including when patients have substance use disorders or cognitive impairment, and is essential for treatment planning when patients require a high level of assistance or supervision because of impaired function or unstable behavior. Family members and others who know the patient well may provide important information about the patient's personality before the onset of illness, since the patient's own account may be unduly influenced by his or her mental state. Collateral sources of information may also provide essential information about the illness course (Section III.C), the current symptoms and behavior (Section III.B), and the reasons for the evaluation (Section III.A). The extent of the collateral interviews and the extent of prior record review should be commensurate with the purpose of the evaluation, the complexity of the clinical presentation, and the diagnostic and therapeutic goals. For example, in an acute inpatient or emergency setting, collateral information may be crucial to developing an understanding of the patient's clinical condition, whereas in long-term outpatient psychotherapy the impact on the treatment process of obtaining collateral information from family or others needs to be considered. Except when immediate safety concerns are paramount, the confidentiality of the patient should be respected. At the same time, it is permissible for the psychiatrist to listen to information provided by family members and other important people in the patient's life, as long as confidential information is not provided to the informant (Sections I.A, I.B, II.C, and V.A).