Background: The hypothesis about the (ab)use of the parasympathetic nervous system to suppress emotions is an idea that, when a person experiences emotions which are perceived as inappropriate to show and/or experience in their social environment, the person will use their own autonomic nervous system in an analogously pathological way in order to „adapt“ to these pathological societal expectations. Very soon (too soon) after the sympathetic activation, which is a natural physiological component of the emotion, the person will coactivate the parasympathetic nervous system as well, in order to camouflage the visible consequences of sympathetic activation and to thereby meet societal expectations. This hypothesized process is likely to drain and unbalance the autonomic nervous system, and a weak and imbalanced autonomic nervous system is both a precursor and correlate of many physical disorders, including essential hypertension and cardiovascular disorders in general. Therefore, it is possible that the presumed mechanism of (ab)using the parasympathetic nervous system to suppress emotions has a role in the etiology of essential hypertension and other cardiovascular disorders. Method: On a sample of 74 middle-aged female participants, 38 normotensive and 36 hypertensive, cardiovascular and autonomic reactivity to display of a human relationship characterized by love and acceptance and to stress caused by ostracism (Cyberball), chronic values of parasympathetic activity, sympathetic activity, chronic blood pressure, emotion suppression tendencies and negative affect were measured. The recruitment criteria for hypertensive participants were physician-diagnosed hypertension and use of 4 or fewer antihypertensive drugs. Values of autonomic activity (RFa and LFa) were determined by spectral analysis of interbeat intervals combined with the input on respiration frequency. In addition to RFa as a measure of parasympathetic activity and LFa as a measure of sympathetic activity, their ratio (LFa/RFa) was also used in the data analysis. Chronic blood pressure was measured using a 24-hour blood pressure Holter measurement, and in participants for whom this measurement was not available, using one measurement of blood pressure in a relaxed state. Emotion suppression tendencies were measured by BEAQ (Brief experiential avoidance questionnaire), ERQ-ES (subscale „expressive suppression“ of the Emotion regulation questionnaire) and DS14-SI (subscale „social inhibition“ of the DS14 questionnaire). Negative affect was measured by PANAS-NA (subscale „negative affect“ of the Positive and Negative Affect Schedule), DS14- NA („negative affect“ subscale of the DS14 questionnaire) and ASI (Anxiety Sensitivity Index). In addition, several measures of stress were applied, including PSS (Perceived Stress Scale) and a measure of life satisfaction. Finally, information was collected on various symptoms and disorders, physical activity, smoking, and alcohol consumption. Results: As expected, chronic RFa and LFa values of normotensive participants (LFa=4.1, RFa=4.2) were statistically significantly higher than chronic RFa and LFa values of hypertensive participants (LFa=2.2, RFa=2.2) (pLFa-C<0.001, pRFa-C=0.020). However, there were no statistically significant differences between the two groups in the frequency of ANS disorders, anxiety, and/or depression, and, when hypertension was excluded, in the frequency of various physical symptoms and disorders. Hypertensive and normotensive participants also did not differ in the intensity of general negative affect (PANAS-NA and DS14-NA), anxiety sensitivity (ASI), stress (PSS), physical activity and frequency of tobacco and alcohol use. Regarding the autonomic and cardiovascular responses to love and acceptance, both the systolic and diastolic blood pressure and the LFa/RFa ratio in both groups statistically significantly increased, and in hypertensives, also the heart rate statistically significantly increased. Altogether, this indicates that the display of love and acceptance aroused intensive emotions, including sympathetic activation, and, as a consequence, increase in blood pressure and heart rate. Also, this pattern of autonomic and cardiovascular responses did not seem to imply that emotion suppression occurred. Regarding the autonomic and cardiovascular responses to love and acceptance, the diastolic blood pressure and the LFa/RFa ratio in both groups statistically significantly increased, and in hypertensives, also the heart rate statistically significantly increased. Altogether, this indicates that the display of love and acceptance aroused intensive emotions, including sympathetic activation, and, as a consequence, increase in blood pressure and heart rate. Also, this pattern of autonomic and cardiovascular responses did not seem to imply that emotion suppression occurred. Regarding the cardiovascular responses to ostracism/Cyberball in hypertensives, they were incongruent: systolic blood pressure increased (indication of sympathetic activation), diastolic blood pressure remained the same, and heart rate decreased (indication of parasympathetic activation). Regarding the autonomic responses to ostracism/Cyberball in hypertensives, LFa/RFa ratio decreased, which is indicative of a parasympathetic activation. Also, there was a moderately high correlation (rho=0,56, p<0,001) between (1) a measure of increase of LFa value after exposure to ostracism in comparison to LFa value before exposure to ostracism and (2) a measure of increase of RFa value after exposure to ostracism in comparison to RFa value before exposure to ostracism. On the whole, the described pattern of autonomic and cardiovascular responses to ostracism could be a result of sympathetic and parasympathetic coactivation, i.e. of abusing the parasympathetic nervous system to suppress emotions. Cardiovascular responses to ostracism/Cyberball in normotensives appeared to be „neutral“: both blood pressure (systolic and diastolic) and heart rate remained the same. With regard to autonomic responses, there was no correlation between (1) a measure of increase of LFa value after exposure to ostracism in comparison to LFa value before exposure to ostracism and (2) a measure of increase of RFa value after exposure to ostracism in comparison to RFa value before exposure to ostracism, which indicates that the ANS activity also remained the same. However, similarly to hypertensives, the LFa/RFa ratio decreased, which is indicative of parasympathetic activation. Overall, this could indicate that Cyberball did not elicit any intensive emotions in normotensives. On the other hand, Cyberball has been proven to be a very reliable stressor, (ostensible) lack of cardiovascular responses to stress could potentially be achieved by abusing the parasympathetic nervous system to suppress emotions caused by stress, the intensity of emotion suppression tendencies in normotensives was substantial and equal to those present in hypertensives, and ANS of normotensive participants was stronger and therefore more able to efficiently camouflage stress responses than it was the case with hypertensives. Conclusions: The results of this study suggest that it is possible that the parasympathetic nervous system is being (ab)used to counteract the consequences of sympathetic activation in the overall experience of emotion. Therefore, it is possible that this hypothesized mechanism contributes to exhaustion and imbalance of ANS and has a role in the etiology of essential hypertension and other cardiovascular disorders.