Assessing patient beliefs in a clinical trial of Hypericum perforatum in major depression

Little is known about the beliefs of patients suffering from major depression as to the causes of their illness and effective treatments. This study introduces a new instrument for capturing these beliefs, the Explanatory Model for Depression (EMD) Questionnaire, and explores the beliefs of patients participating in a clinical trial of an alternative medicine, Hypericum perforatum. Although the EMD was originally conceptualized as having five factors pertaining to models of the illness and treatment approaches, the data suggest that patient beliefs are aligned on two factors pertaining to internal and external locus of control. Strong beliefs on either of the EMD locus of control subscales are associated with more severe depression. More importantly, strong beliefs on the external locus of control subscale are associated with less improvement over the 8-week period of observation. These results support the role of patients' beliefs in their recovery from depression and suggest that patients who believe the causes of their depression are outside of their control are less likely to improve over time. It is important to note that beliefs did not mediate the effect of treatment on depression in this study, perhaps because patients were blinded to their treatment condition. Future studies should explore whether patient beliefs have an even greater impact when patients are aware of the treatment they are receiving and can determine whether that treatment is consistent with their beliefs.