Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Counseling Psychology & Community Services


This study examined the impact of time of day of testing and subjectively measured daytime sleepiness and nighttime sleep on memory performance in adults with multiple sclerosis (MS) and in unimpaired adults. Thirty-four multiple sclerosis subjects (a.m.; N=17 and p.m.; N=17) and forty controls (a.m.; N=16 and p.m.; N=24) were assessed using the Logical Memory, Visual Reproductions, and Digit Span subtests of the Weschler Memory Scale-Ill, California Verbal Learning Test, and several questionnaires about mood, sleep, and physical symptoms. The primary result of this study was the absence of significant differences between the multiple sclerosis participants and controls on many of the neuropsychological tests. A possible explanation for the absence of findings may be related to all of our multiple sclerosis participants being high functioning in that they transported themselves to the lab for testing. The literature suggests it is common to not find glaring differences between multiple sclerosis participants and controls across many neuropsychological tasks. Additionally, daytime and nighttime sleep factors were not found to be significant factors in this study. Future research should continue to look at time of day factors related to multiple sclerosis in an attempt to optimally and accurately test individuals with this disabling disease. Limitations and future direction are also discussed.