Biochemical and circulatory parameters during purely mental stress.

In order to evaluate biochemical and circulatory parameters during purely mental stress, 20 healthy medical students were studied before, during and at the end of an important written medical examination. Plasma catecholamines and diastolic blood pressure rose significantly during the examination, whereas systolic blood pressure did not change and heart rate declined. Continuous ECG recording in 12 of the subjects showed a high peak in heart rate at the start of the examination, quickly followed by a rapid decline to values seen on the previous day. It is suggested that in mental stress without physical effort, the enhanced sympathetic activity triggers an increase in parasympathetic activity which overrides the circulatory effects of the former.