Snæfríður Guðmundsdóttir Aspelund will present and discuss her PhD thesis, “Stress & Cognitive Function: Exploring the Impact of PTSD and Breast Cancer on Cognition and the Potential Benefit of Bright Light Therapy” on Wednesday, January 30th at 3:00 pm. Snæfríður has already defended her thesis in a closed session.

Abstract

Cognitive function—the ability to learn, solve problems, and effectively use stored information—is essential for everyday activities. While many factors contribute to cognitive impairment, this Thesis specifically examines the often-overlooked influence of stress. Major life stressors (e.g., war exposure, sexual violence, cancer diagnosis and treatment) can cause posttraumatic stress disorder (PTSD), and affect biological (e.g., cortisol) and psychological (e.g., depressive symptoms) stress markers known to impair cognitive function. Given the significant negative impact of cognitive impairment on individuals and society, the overarching goals of this Thesis were to a) further investigate the relationship between life stressors and cognitive impairment, b) identify potential moderators of this relationship and c) explore whether circadian-stimulating bright light therapy (BLT) can mitigate the negative effects of life stressors on stress markers, and cognitive function. The three papers listed below highlight the main aims and findings of this Thesis.

In Paper I, a multilevel random effect meta-analysis was conducted to investigate the relationship between PTSD and cognitive impairment, along with potential moderating factors. Literature search yielded 54 peer-reviewed relevant studies in which this relationship was examined. Age, study design, study population, neurocognitive outcome assessed, gender, study quality, type of PTSD measure, as well as the presence of comorbidities such as traumatic brain injury, depression, and substance use, were investigated as potential moderators. The results suggested that PTSD is associated with both cognitive impairment and neurocognitive disorder, compared to healthy controls (HC), demonstrating a consistent link that persisted across all examined moderators.

Paper II examined cancer-related cognitive impairment (CRCI) among women undergoing the life stressor of breast cancer (BC) diagnosis. Previous studies primarily examined chemotherapy's effect on CRCI, while this study aimed to assess CRCI in women with BC before any treatment and explore potential associations with stress. A population-based study with 112 treatment-naïve women with BC and 67 HC was conducted. Cognitive function was assessed via neuropsychological assessment. Cognitive complaints and psychological stress markers (i.e., cancer-related stress (related to PTSD), depressive and anxiety symptoms) were measured with a self-report battery. Biological stress markers (i.e., cortisol and α-amylase) were collected from saliva. The findings revealed that treatment-naïve women with BC had greater impairments in processing speed and verbal memory, along with more frequent cognitive complaints than HC. Multilinear regressions showed that a) steeper α-amylase slope, younger age and lower overall cancer-related stress were associated with better overall cognitive performance, and b) greater depressive symptoms were associated with more frequent cognitive complaints. These findings indicate that CRCI can start before BC treatment and that stress could contribute to it.

Paper III builds on the findings from Papers I and II, indicating that life stressors may contribute to cognitive impairment by affecting stress markers. Since the cancer itself and surgery can trigger stress responses and disrupt circadian rhythms, further increasing the risk of CRCI, Paper III explored whether BLT could mitigate the negative effects associated with BC (including BC surgery) on cognitive function and stress. A double-blind, randomized controlled trial was conducted with the same participants and measurements as in Paper II. Participants were randomly allocated to receive circadian-stimulating bright white light (BWL, N = 60) or non-circadian-stimulating dim white light (DWL, N = 57) for four weeks post-BC surgery. Linear regression and path analyses indicated that the BWL group reported significantly fewer cognitive complaints. Additionally, there were non-significant trends, with small to medium effects, for faster reaction times, as well as lower levels of both overall cancer-related stress (related to PTSD) and intrusive thoughts in the BWL group compared to the DWL group.

Overall, the results of this Thesis emphasize the importance of monitoring cognitive function in individuals exposed to major life stressors and an early intervention when needed. Future studies should further investigate BLT's potential in ameliorating cognitive impairment and stress among individuals experiencing major life stressors and explore the underlying mechanisms.

Keywords: Cognitive function, stress, post-traumatic stress disorder, cancer-related cognitive impairment, light therapy