This study examined the capacity of severely depressed outpatients to consent to DBS research, evaluated the associations between depression severity and therapeutic misconception, and investigated misconceptions regarding this novel treatment modality. Even in a highly selected TRD sample, subjects showed very good performance across all domains of decisional capacity. On a scale measuring therapeutic misconception, however, some subjects tended to view the study’s purpose as directed specifically at helping the subjects involved, rather than exploring the efficacy of an experimental intervention; to underrate the risks of the neurosurgical intervention; and to overrate the likelihood of personal benefit and degree of individualization of their care in the study. Therapeutic misconception scores suggested that subjects who were more depressed might have had fewer misconceptions about the nature of the research study, a potential relation-ship warranting further exploration in larger and more heterogeneous samples.
Concerns about the capacity of depressed patients to consent to research are not new.20
Repeatedly, though, studies have failed to find substantial impairments in the decisional capacity of people with psychiatric disorders to consent to research,25,39
including studies that evaluated severely depressed inpatients and those requiring electroconvulsive therapy. 26,27
Although the MacCAT-CR is individualized for each investigation, which limits the validity of quantitative comparisons across studies, it is notable that participants in this study, representing a sub-set of extremely depressed individuals, performed extraordinarily well on all MacCAT-CR capacity measures. Indeed, most subjects achieved perfect or near-perfect scores. In part, this may be due to the intensity and quality of the informational process to which prospective DBS subjects were exposed. It bears noting, however, that seven subjects did not score perfectly on the “major risks” item of the understanding subscale, suggesting that this section could benefit from greater emphasis during consent discussions. That said, taken together, these findings suggest that the persistence and prevalence of concerns about the capacity of depressed patients to consent to research may be disproportionate to the real risks, as long as adequate safeguards and sufficient information are present. Given the consistency of these findings, the research community should consider whether most individuals with psychiatric disorders are actually as vulnerable to decisional impairments as they are commonly portrayed,20
or if such concerns might instead be a reflection of the widespread stigma and prejudice against psychiatric disorders.
This study further demonstrates that, when asked to elaborate on rating-scale responses regarding study purpose, risks, and benefits, participants generally evidenced a grasp of the purpose of the study as testing a new therapeutic modality for its safety and efficacy; that there were risks to surgery, particularly brain surgery; and that personal benefit was not guaranteed. There were clearly varying levels of sophistication in these responses from this highly selected group of participants who may not be representative of the level of research sophistication of most depressed individuals.
Participants expressed an interesting range of responses when asked to reflect on their ratings of their level of altruism. Some clearly endorsed the desire to help themselves first, with altruism being only a secondary consideration. Others more directly stated that they wanted other people not to suffer as they had, or that they wanted to contribute or give meaning to their suffering. These sorts of responses do not seem distinctly different from those seen in patients with other serious illnesses—for example, advanced cancer patients who volunteer for early-phase clinical trials.30
Nevertheless, this study also reinforces the message that even decisionally capable subjects may have problematic—even mistaken—beliefs about clinical research. The degree of therapeutic misconception found in these subjects (64.5%) is comparable with findings from similar studies conducted in psychiatric and nonpsychiatric populations, suggesting that this population is not uniquely susceptible to therapeutic misconception.32,33,37,38
As noted elsewhere, educational approaches focused on the differences between research and treatment— including the use of educators not directly involved in the study—may help subjects avoid therapeutic misconception and better understand the nature of the clinical trial in which they are enrolled.37
However, social forces relevant to DBS may present additional challenges. The extensive media coverage of DBS for TRD, ranging from unrealistic expectations about the brain’s newfound “happy switch”40
to alarmism about “psychosurgery redux,” 41
highlights the ways in which distorted views of the procedure may enter the public imagination. Extra vigilance and effort on the part of the scientific community to promote public understanding are thus required to combat broader misunderstandings about this novel intervention, as well as to foster better understanding of the purpose and limitations of clinical research. The fact that subjects in this study exhibited very good performance on measures of decisional capacity but still showed evidence of common misconceptions indicates that refinements and elaborations of the consent process alone may not be sufficient to remedy these misunderstandings and counteract the forces that operate at broader levels to drive overall public understanding.
It is interesting that there was a trend toward a negative correlation between baseline depression ratings and total therapeutic misconception score, i.e., subjects who were more depressed demonstrated fewer misconceptions about the nature of the research study. They also showed lower levels of concern about the low-risk aspects of the study (MRI scans and neuropsychological testing). These findings might be a reflection of depressive realism
the idea that depressed individuals make more accurate judgments than their nondepressed counterparts. On the other hand, more recent studies of this phenomenon have called the idea of depressive realism into question, suggesting that clinically depressed individuals make negatively distorted judgments.43
Particularly given the limitations of this study noted subsequently, further work on this question is warranted.
Among this study’s limitations is that this sample comprised a small, prescreened, well-educated subset of subjects with TRD. Subjects also had to be highly motivated to participate in the study’s demanding procedures—in some cases, they would have to move to a new city to participate. Moreover, our subjects’ desire to be in a study of DBS for TRD may have influenced their responses, i.e., they may have been concerned that admitting to the “wrong” motivations would compromise their ability to remain in the study (although we found multiple instances of subjects providing frank assessments of their motivations and desperation). In addition, the validity of our findings may be limited by the absence of validated measures for several of the concepts that we sought to assess, including desperation and altruism. Similarly, the scale used to measure therapeutic misconception, although theoretically grounded and based on those used in previous studies, had not been validated. Finally, there was no control group, making it difficult to know the extent to which other variables may have accounted for our findings.
Further studies are needed to examine decisional capacity and therapeutic misconception across a broader sample of participants with TRD. There is also a need for further methodological refinement and validation of tools to assess influences on decision making. It might be most useful to compare TRD subjects with those with other serious illnesses considering early phase or invasive research in an effort to identify which, if any, of the phenomena we explored are specific to DBS for TRD research. This is particularly important at a time when multiple brain-based interventions—for example, gene therapy trials that include sham surgery—are being mounted for a variety of neurological and neurodegenerative disorders.