Consent Through Rose-Tinted Glasses: The Optimistic Bias in Parkinson's Disease Clinical Trials

摘要

Phase I clinical trials for Parkinson's disease (PD) are a necessary first step in developing better treatments for future patients. Like Phase I cancer trials, Phase I trials in PD can involve significant risks with little to no prospect of direct therapeutic benefit to participants. Understanding how patients think about their susceptibility to the risks and benefits associated with these trials is critical for assessing the validity of informed consent in this context. In their article "Ethical Criteria for Human Trials of Stem Cell-Derived Dopaminergic Neurons in Parkinson's Disease," Hurst and colleagues (2015) rightly focus on how factors such as those that give rise to the therapeutic misconception can distort perceptions of risk/benefit and thereby impair informed consent. However, they fail to address how other factors, such as the optimistic bias, may also pose special ethical challenges in this context. This omission is significant for two reasons. First, the optimistic bias is a factor that has been found to distort appreciation of risk/benefit information among participants of other types of early-phase clinical trials (Jansen et al. 2011). Second, research in neuroscience has shown that drugs that enhance dopaminergic function (e.g., L-DOPA) also engender the optimistic bias (Sharot et al. 2012). These findings suggest that patients recruited to early-phase PD trials, who are commonly taking dopaminergic medications, may be especially vulnerable to the optimistic bias and in turn fail to fully appreciate risk-related information. This commentary discusses the neurobiology of the optimistic bias and its ethical significance for early-phase research on PD.