Law and Human Behavior, Vol. 15, No. 4, 1991 Mentally Ill and Non-Mentally-Ill Abilities to Understand Informed Disclosures for Medication* Patients' Consent Preliminary Data Thomas Grisso and Paul S. Appelbaum* The performance of two groups of hospitalized mentally ill patients (schizophrenia and major depres- sion) and two groups of non-mentally-ill patients (patients hospitalized for ischemic heart disease and non-ill primary care patients) was compared on a standardized, objective instrument for assessing patients' understanding of information relevant for patient decision making (consent) about treatment with medication. Generally, hospitalized schizophrenic patients manifested significantly poorer un- derstanding of "informed consent" disclosures about potential medication than did the other groups. Considerable variance, however, was apparent within the schizophrenic group and was related to a number of clinical and demographic variables. The results are interpreted with reference to issues of competence to consent to or refuse treatment. Mental health law, as a distinct body of law, has been premised on the presump- tion that mentally ill persons, as a group, differ from non-mentally-ill people in their decision-making abilities. The decisions at issue may include choices about whether to seek hospitalization, to spend money, to marry, or to write a will. In each of these cases, and others, the law has treated mentally ill persons differ- ently, believing that they are more likely to manifest impaired decision-making abilities than are people without mental illness. * This research was supported by the Research Network on Mental Health and the Law of the John D. and Catherine T. MacArthur Foundation. We wish to acknowledge Cynthia Wickless, Elizabeth Cote, and Kathryn Cranford for their assistance in this study and to thank several colleagues for helpful comments on an earlier draft: William Gardner, Steven K. Hoge, John Monahan, Stephen Morse, Ed Mulvey, and Henry Steadman. Requests for reprints may be sent to either author at the Department of Psychiatry, University of Massachusetts Medical Center, 55 Lake Avenue North, Worcester, MA 01655. 377 0147-7307/91/0800-0377506.50/0 9 1991 Plenum Publishing Corporation