Personality, Stress and Cold Sores: A Twin Study

Results of a previous pilot study about oral herpes in twins suggested that there are genetic factors in an infected person that strongly influence the reactivation (waking up) of the HSV-1 virus from a dormant (sleeping) state to cause cold sores. The purpose of this study was to understand how the genes of the host, and environmental factors such as stress and personality, contribute to how a person’s body responds to oral herpes infections. A twin study was done because it is the ideal way to understand how genetic and environmental factors contribute to a condition.

Fifty pairs of twins who both tested positive for the HSV-1 virus were recruited for this study. The study involved 4 visits to the University of WA Virology Research Clinic over a period of 2 months. The first visit lasted about an hour. At the first visit, a brief medical history was taken, and about 3 teaspoons of blood were drawn from each twin to determine if they had been infected by the HSV-1 virus. If both twins were found to be eligible at the first visit, they were invited to return to the clinic for 3 more visits: an enrollment visit and two follow-up visits.

During the enrollment visit, additional blood was drawn, and the clinician showed the participants how to collect saliva at home using a swab similar to a “Q-tip.” The swabs were used to measure the amount of HSV-1 in their saliva. Participants were asked to collect one swab each day at home for 60 days. During this time period, they also completed a daily diary to record any symptoms they were experiencing. Participants returned to the clinic on day 30, and brought in the first 30 swabs and their symptom diaries. Additional blood was drawn at the 30-day visit. Participants returned again on day 60 with the swabs and their symptom diaries for the last 30 days of the saliva collection.

Stress and personality were also studied. Participants completed daily questionnaires about their stress that day, as well as a weekly stress log and a monthly stress checklist. At the beginning of the study, participants completed a questionnaire about personality traits.