Capacity to consent to research among patients with bipolar disorder

Experts have debated the influence of mental illness on decision-making capacity. This paper reviews concepts of decision-making capacity and existing research on the influence of mental illness on capacity to consent to research. We propose how bipolar disorder, especially mania, may have an effect on consent capacity. The current conceptualization of capacity utilizes legal standards of 'choice', 'understanding', 'appreciation' and 'rational reasoning', as well as voluntarism, or the assurance that the patient is free to agree or to decline to participate in research. Studies of patients with schizophrenia suggest impaired cognition influences 'understanding' and is more important than severity of psychosis in affecting decision-making abilities. There are no studies of sources and extent of impairment to consent to research among manic patients. Mania may influence a patient's understanding of the research protocol, but also alter the patient's views, values and level of insight, thus impairing decision-making abilities at the 'appreciation' standard even when the patient understands the relevant information. Mania may impact freedom to decide, yet paradoxically, manic patients may be less influenced by others and less vulnerable to coercion, undue influence and undue incentives compared to patients without mental illness. We suggest that in patients with mood disorders, the legal standard of appreciation be thoroughly probed during the consent procedure. Studies of the effect of mania and depression on consent capacity and voluntarism are needed in order to develop processes that increase safeguards in the informed consent process.