The diurnal rhythms of subjective wakefulness and anxiety
Defined as "heightened brain activity and increased physiological responding" (Gatebel, Baum, & Krantz, 1989, p. 37), arousal has been conceptualized as a continuum. Both anxiety and wakefulness are forms of arousal modulated by central nervous system and neuroendocrine mechanism. Through the waking day, wakefulness varies in a distinctive bimodal rhythm with late morning and afternoon peaks separated by a mid-afternoon dip, or "siesta". The present study examines the relationship between the daily rhythm of subjective wakefulness and that of subjective anxiety in a non-clinical sample of students. Specifically, it is asked: Does the Level of anxious arousal co-vary with levels of wakefulness? It is predicted (1) that a bimodal pattern of wakefulness with a marked siesta effect will be found for anxiety and wakefulness, (2) that a diurnal rhythm will be found for anxiety, and (3) that anxiety will vary in a negative relationship to wakefulness. Using scores on the Spielberger State-Trait Anxiety Inventory Form Y - Trait Version, 46 undergraduate volunteers were divided into high- and low-anxiety groups. Every hour for 2 days subjects filled out questionnaire packets including the Stanford Sleepiness Scale (SSS), the 2-dimensional Affect Grid comprising measures of sleepiness-arousal. (Grid-A) and unpleasant-pleasant feelings (Grid-P), and the State-Trait Anxiety Inventory-State Version (STAI-S). The expected bimodal pattern was seen for alertness in both groups on both measures. However, no diurnal rhythm was found for the STAI-S in either group. Therefore, the arousal measures and the STAI-S were not found to co-vary. It was found, however, that the HI-A group experienced a markedly higher sleepiness level through the day. Levels of wakefulness on both SSS and Grid-A were significantly lower ( p < .05). It can be inferred, then that anxiety and sleepiness are related, even though anxiety levels do not appear to be modulated by wakefulness/sleepiness in a diurnal pattern. Further research should examine the sleep quality of anxious persons using objective measures and the outcome of treatments aimed at both sleep disorders and anxiety disorders on the other form of arousal.