Premenstrual syndrome (PMS) is a clinical entity of concern in women of reproductive age group with its onset during the late luteal phase of the menstrual cycle that typically resolves within a few days after the onset of menstruation. Female reproductive hormones stimulate the gene promotor region of Gonadal steroids, which are modulators of the hypothalamic-pituitary axis, in association with the autonomic nervous system (ANS), form the stress system, which regulates the homeostatic mechanisms of the body. Disruption of this mechanism can lead to sympathovagal imbalance and cognitive deficits. Objectives: This study was aimed to compare the autonomic functions and cognition between PMS and control group. Methodology: This cross-sectional study was conducted as a pilot study with 20 subjects in each group. Autonomic function test and P300 were recorded. Study participants were also asked to answer Montreal cognitive assessment (MOCA) questionnaire. Results: On comparison of the test results between the two groups, individuals in PMS group were found to have increased sympathetic activity and reduced cognition when compared to the no PMS (control) group. Conclusion: The findings from this study proves a detrimental effect of gonadal steroids on autonomic nervous system and cognition.