To assess how expectations and symptom beliefs based on a previous episode of insulin-induced hypoglycemia influence symptom awareness after a second insulin injection in healthy subjects.
After a first episode of insulin-induced hypoglycemia in session 1, half of 40 healthy male subjects were told at the beginning of session 2 that they would receive human insulin (0.05 IU/kg), the other half saline. According to a 2 × 2 balanced placebo design, only half of each group received the announced substance, whereas the other half received the substance contrary to their expectations. Data collection at 10–15 min intervals included a symptom checklist, blood pressure, heart rate, plasma glucose, and counterregulatory hormone levels.
The expectation of a repeated hypoglycemia clearly influenced the subjects' psychophysiological responses. Without knowledge about the actual treatment, there was only an average maximum confidence of 65% of having received insulin. Expecting the insulin injection led to an increased sum score of neuroglycopenic symptoms but not of autonomic symptoms. Subjects expecting the insulin injection reported more weakness, blurred vision, and inner restlessness than those subjects expecting the saline injection. Those subjects correctly informed about receiving insulin experienced the most drowsiness, dizziness, and headaches. The expectations of the insulin injection increased the norepinephrine levels and the heart rate. The told insulin/given insulin group showed the highest glucagon levels.
The results support the hypothesis that the subjects' expectations influence their perceived symptoms.
