Who volunteers for phase I clinical trials? Influences of anxiety, social anxiety and depressive symptoms on self-selection and the reporting of adverse events.

OBJECTIVE: To investigate the influence of anxiety, social anxiety and depressive symptoms on the willingness of healthy subjects to volunteer for phase I studies and to report adverse events.
MATERIALS AND METHODS: A group of healthy subjects who had never participated in a clinical trial ("Naïve Subjects") were invited to participate in a phase I study. All subjects were assessed for trait anxiety (State-Trait Anxiety Inventory, STAI-T), social anxiety (Social Avoidance and Distress, SAD, and Fear of Negative Evaluation, FNE) and depressive symptomatology (Beck Depression Inventory, BDI-II). Subjects who accepted the invitation to participate were compared with those who refused. The personality traits of a group of "Actual Participants" were examined, and the relation of these traits to adverse events reported during participation was evaluated.
RESULTS: A significant inverse correlation was found between the STAI-T (R = -0.203, p < 0.05) and SAD (R = -0.204, p < 0.05) scores and the willingness to participate. Naïve Subjects who refused the invitation to participate showed higher scores on STAI-T (Z = -2.600, p < 0.01) and SAD (Z = -2.524, p < 0.05) inventories. Logistic regression using BDI-II, STAI-T, SAD and FNE as covariates also showed that the only unique predictors of participation were the STAI-T (p < 0.05) and SAD (p < 0.01) scores. Significant positive correlations were found between trait anxiety and reporting of adverse events.
CONCLUSION: Participants in phase I studies are a self-selected sample defined by low trait-anxiety and social avoidance behaviors. This self-selection bias may affect the study results because less anxious subjects tend to report fewer adverse events. The characterization of a participant's personality traits may be important in phase I studies.