Junior, human health major
My Research Project
Post-traumatic stress disorder (PTSD) is a debilitating mental illness that heavily impacts an individual’s physical, mental and emotional health. One overlooked, but very important, consequence of this illness is that individuals with PTSD have an increased risk of developing hypertension and cardiovascular disease1. Past research has revealed that those with PTSD have an exaggerated blood pressure and heart rate response and a blunted heart rate variability response to acute mental stress1. While these studies have improved our understanding of PTSD and the physiological effects it has, they don’t highlight a very important factor: the possibility that it affects men and women differently.
PTSD studies have typically been either all men, or a very few women included in a mostly male population. The research has produced results that primarily focus on male reactivity2, andhas neglected an entire demographic of PTSD victims that seem to have a different response. While men and women have a similar rate of experiencing traumatic events, women are twice as likely to be diagnosed with PTSD3. In addition, healthy premenopausal women have a lower risk of developing cardiovascular disease compared to men, although once diagnosed with PTSD, this risk increases three times, placing the women at higher risk3. Given these biological differences, the purpose of this study was to determine if there is also a sex difference in autonomic and cardiovascular responses to acute mental stress in individuals who have PTSD.
Our study consisted of 33 individuals— 15 women and 18 men—for a total of two visits. The first visit was a screening where we took the volunteers’ vital signs, gave them PTSD surveys to determine the severity of their condition and checked for exclusion criteria to ensure they could be in the study. The second visit was a micro visit, where we recorded experimental data. We measured the study subjects’ blood pressure, heart rate and muscle sympathetic nerve activity at baseline, then those same recordings during three minutes of mental stress. Beat-to- beat blood pressure was recorded using a continuous noninvasive arterial pressure (CNAP) monitor and heart rate was recorded via an electrocardiogram (EKG). Muscle sympathetic nerve activity (MSNA) was recorded via the microneurography procedure. Mental arithmetic served as our mental stressor: the participants subtracted a given number from a numbered index card continuously for three minutes while a “coach” was pressuring them to give an answer as quickly as possible.
At baseline, measurements for age, body mass index, clinician-administered PTSD scale (CAPS) and PSTD checklist–military version (PCLM) survey scores, blood pressure and heart rate variability were all comparable between the sexes. However, MSNA was significantly different. This was a very interesting find, as we were not anticipating this result. In healthy populations, men have a higher MSNA at rest than women. Based on this data, it seems that women with PTSD have a higher resting MSNA than men. In response to mental stress, systolic arterial pressure was higher in women than men, while diastolic arterial pressure was comparable between the two groups. In addition, heart rate seemed to be higher in women than men, but had not reached significance, although MSNA in response to mental stress was significantly higher in women compared to men. Even more interesting was the root mean square of the successive differences (RMSSD), the time domain measurement of parasympathetic nervous system activity, was comparable between both groups, but the high frequency domain for parasympathetic response showed women having a decreased response to mental stress than men.
In conclusion, resting MSNA was significantly higher in the women than the men. Systolic arterial pressure reactivity to mental arithmetic as higher in women with PTSD compared to men, while diastolic arterial pressure reactivity was comparable between the groups. Heart rate was comparable between women and men with PTSD. MSNA reactivity to mental stress was higher in women than men while heart failure response was blunted in women compared to men suggesting greater dysregulation of the autonomic nervous system in women with PTSD. RMSSD was comparable between men and women in response to mental stress.
In summary, women with PTSD in our study have an increased blood pressure and sympathetic response in addition to a blunted parasympathetic response to acute mental stress. These results provide insight into the mechanisms that are associated with a higher risk of cardiovascular disease in women with PTSD.
Realities of Research
Doing research in a lab was very different from my high school research experiences. For one, this was a clinical lab, so I was working with people every day, which was a rewarding experience. Also, my lab team was made up of very intelligent, cohesive and welcoming individuals, so during every study I was able to learn something new while having a good time. I also had to learn how to set up the lab for the studies we would be conducting, so I had to understand the procedure being performed and how to prepare for it. For example, one procedure we performed was microneurography— a qualified lab member inserted a tungsten electrode into the participants’ peroneal nerve to record sympathetic activity.
What surprised me about the experience was how often research doesn’t go as planned, especially when working with people. Some study participants wouldn’t come in to the lab as scheduled, or if they did, they didn’t want to go forward with certain procedures for a variety of reasons. Because of this, some patients didn’t have all of the data I anticipated collecting, but that was just a part of the research process.
As for our results, it was very rewarding to see my hard time and effort come to fruition. Some of the results I expected, but others I wasn’t expecting at all. Honestly, each result made the experience all the more exciting.
Life as a Scientist
Life this summer was challenging, but rewarding. I experience many exciting things that have provided me with good memories. The feeling that I felt once I formed graphs based on my data was great and was the best part of the experience; it was the result of my hard work and dedication to my project.
The worst part of the experience would have to be the hours I spent trying to understand certain topics by myself. While learning more about what I am doing interested me, there was some information I needed to know but took me a little while to grasp, which often annoyed me. However, once I did understand it, the passion I had for my project increased. Finally, my lab team was instrumental in me developing this project, especially my mentor. Her mentorship has taught me so much during the weeks I spent with her this summer and I am excited to learn even more.
- Edmondson D, von Kanel R. Post-traumatic stress disorder and cardiovascular disease. The Lancet Psychiatry 2017;4:320-9.
- Park, J., Marvar, P. J., Liao, P., et al. (2017). Baroreflex dysfunction and augmented sympathetic nerve responses during mental stress in veterans with post-traumatic stress disorder. The Journal of Physiology, 595(14), 4893–4908. doi:10.1113/JP274269
- Kubzansky LD, Koenen KC, Jones C, Eaton WW. A prospective study of posttraumatic stress disorder symptoms and coronary heart disease in women. Health psychology : Official Journal of the Division of Health Psychology, American Psychological Association 2009;28:125-30.
Touré Jones is a junior majoring in human health at Emory University in Atlanta. He is a 2019 Short-Term Research Education Program to Increase Diversity in Health-Related Research (STRIDE) Fellow working in Dr. Jeanie Park’s lab also at Emory University. Touré’s fellowship is funded by APS and a grant from the National Heart, Lung, and Blood Institute (Grant #1: R25 HL115473-01). After graduation, Touré plans on attending medical school to pursue his dreams of being a physician.