Capacity to consent to research in schizophrenia: the expanding evidence base.

Capacity to consent to research, fundamental to informed consent and thus vital to the ethical conduct of research, may be impaired among a variety of research populations. Until recently, relatively little empirical evidence has been available to inform discussion and policy-making regarding whose capacity should be assessed, what should be measured, and how it should be measured. Capacity to consent to research has emerged as a central topic in the field of "empirical ethics," an important area of biomedical research devoted to bringing evidence-based methods to the study of ethically salient issues in biomedical and biopsychosocial research. In this paper, empirical studies of capacity to consent to research are reviewed, with a particular focus on studies involving people with schizophrenia. These studies provide intriguing data regarding the nature, correlates, and modifiability of decisional abilities among potentially vulnerable research populations, including individuals with serious neuropsychiatric illnesses. Areas in need of further empirical ethics research are highlighted. Copyright (c) 2006 John Wiley & Sons, Ltd.