A study of stress and autonomic nervous function in first year undergraduate medical students.

Psychological stress is a risk factor for hypertension and coronary artery disease. The purpose of this study was to assess the impact of real life stressor, that of stress among first year medical students on cardiac autonomic regulation. Stress levels in 36 non-smoking, healthy first year medical students of either gender were assessed on a self-rating scale. Cardiac autonomic regulation was tested using both conventional tests and spectral analysis of heart rate variability (HRV). Nine subjects who obtained scores on the stress scale in the upper quartile were classified as the "stress" group and the rest constituted the "no stress" group (n = 27). There were no significant differences between the two groups on any of the conventional tests of autonomic nervous activity. The low frequency power in normalized units and low frequency high frequency ratio of heart rate variability in supine posture was significantly higher in the "stress" group compared to the "no stress" group. The low frequency power in normalized units was significantly positively correlated with total stress score. The changes were suggestive of a tilt in the resting cardiac autonomic balance towards increased sympathetic activity.