Background: Informed consent is a key element of ethical clinical research. Patients with serious mental illness may be at risk for impaired consent capacity. Corrective feedback improves within-session comprehension of consent-relevant information, but little is known about the trajectory of patients' comprehension after the initial enrolment session.
Aims: To examine whether within-session gains in understanding after feedback were maintained between study visits and to examine stability of decisional capacity over time.
Method: This was a longitudinal, within-participants comparison of decisional capacity assessed at baseline, 1 week, 3 months, 12 months and 24 months in 161 people with schizophrenia or bipolar disorder.
Results: Within-session gains from corrective feedback generally dissipated over each follow-up interval. Decisional capacity showed a general pattern of stability, but there was significant between-participant heterogeneity. Better neuropsychological performance was associated with better decisional capacity across time points. Positive symptoms of schizophrenia did not predict any aspects of decisional capacity, but general psychopathology, negative symptoms and depression evidenced some modest associations with certain subdomains of decisional capacity.
Conclusions: Informed consent may be most effectively construed as an ongoing dialogue with participants at each study visit.