Informed Consent in Schizophrenia Research

To the Editor: Studies have found that patients with schizophrenia demonstrate impairments that affect their ability to give informed consent to participation in psychiatric research (1-3). However, few studies have compared stable schizophrenic patients with healthy control subjects using real, rather than hypothetical, research protocols.

We conducted a preliminary study of the ability of schizophrenic patients to understand the information in a consent form approved by an institutional review board for a research study involving magnetic resonance imaging (MRI) of the brain. The study thus examined one aspect of informed consent, factual understanding. Participants were 13 clinically stable patients with a DSM-IV diagnosis of schizophrenia or schizoaffective disorder and 13 healthy control subjects. The patients had a mean±SD age of 32±9 years and a mean total score of 45±9 on the Brief Psychiatric Rating Scale, indicating a moderate level of psychiatric symptoms. The mean age of the healthy control subjects was 28±6 years.

Both groups completed a three-item fill-in questionnaire examining the purpose, risks, and procedures involved in the MRI study as outlined in the consent form. Questionnaires were later scored by a psychiatrist blind to the group assignment. The highest possible score was six points. The mean score±SD for the patients with schizophrenia was 4±1.9, compared with 4.5±1.5 for the control group, a statistically insignificant difference. These results indicated that patients with clinically stable schizophrenia were able to comprehend research consent forms to the same degree as healthy control subjects.

Some caveats should be considered when interpreting our findings. The finding of no difference in comprehension between the schizophrenic patients and the healthy control subjects could have been a consequence of a lack of statistical power associated with the small sample size. However, a power analysis revealed an effect size of .23, which suggests that power was not a significant issue.

It is also possible that the consent forms were not detailed enough or were too complicated to allow subjects' comprehension scores to be meaningfully compared. This issue poses an interesting dilemma for researchers, as there are no normative values for what is an acceptable threshold level of basic comprehension for informed consent in research. It should be noted that the consent form in this study was approved by an institutional review board and was felt to be of appropriate depth and clarity for subject comprehension.

The brief questionnaire may not have allowed a detailed assessment of subjects' understanding of the consent form. However, it was designed to be brief because of a suggestion that short questionnaires could be used for low-risk studies, with more questions added as the risk increased (4).

Nonetheless, the results of this preliminary study suggest that patients with clinically stable schizophrenia have a level of factual understanding of research consent forms equivalent to that of healthy controls. Furthermore, questionnaires like the one used in our study can provide documentation of a subject's understanding of the information provided on a consent form. Future studies should examine other aspects of informed consent for research (5) and should further explore, if possible, how patients' capacity to give informed consent compares with that of healthy control subjects.