Effect of social stress on time perception: Role of epigenetic changes

Time perception, in which individual differences are quite remarkable, is very sensitive to the emotions and environment. Although genetic variants are insufficient to explain the inter-individual differences in time perception, epigenetic changes seem promising. In this study, we aimed to investigate the effects of social stress and DNA methylation changes in COMT and DRD2 genes on time perception. To this aim, 44 healthy young adult volunteers (23 Females, 21 Males) were experimentally exposed to acute social stress using Trier Social Stress Test (TSST). Participants were given visual time reproduction task for suprasecond scale (2, 2.5, 3, 3.5 and 4 s) before and after the TSST, and spatial reproduction task as a control. Deviation coefficients (CV) from the target duration and size were calculated to compare participants' time and space perception performances, respectively. Saliva cortisol levels were measured before and after TSST by colorimetric ELISA method in order to reveal paticipants' physiological responses trigered by acute stress. In addition, state anxiety levels at pre- and post-TSST were examined by Spielberger's State-Trait Anxiety Inventory (STAI). Finally, COMT and DRD2 promoter methylations were quantified by pyrosequencing. Psychometric and cortisol measurements confirmed that TSST triggers acute stress response effectively. A repeated measures ANOVA with task, stress and cortisol responses showed that the task main effect was significant and individuals were more precise in the space perception task compared to the time perception task. There was a significant main effect of stress, as well as a significant interaction between stress and task. We observed that people have a tendency to underestimate time intervals under basal conditions. Social stress led to time dilation, causing time percieved as closer to absolute time. However, social stress had no effect on space perception. Our results showed that the rate of increase in cortisol did not have a significant main effect. We found a significant positive correlation between COMT gene methylation level and time perception performance. People with a highly methylated COMT gene showed better time perception performance. By implementing ecologically validated TSST test, our results supported that acute social stress causes distortions in interval timing. Our results suggest that differences in COMT DNA methylation levels in individuals may affect time perception by causing differences in catecholamine levels, particularly dopamine. Based on this, the incerase in time perception performance in response to stress could be due to change in the speed of internal clock and/or cognitive performances icluding working memory and attention. However, our results need to be supported by functional/molecular neuroimaging data to elucidate the possible mechanism.