Night-time thoughts in high and low worriers: reaction to caffeine-induced sleeplessness

There is ample evidence for the existence of an association between sleeplessness and worry. Not much is known, however, concerning the nature of this relationship. Therefore, a study was conducted investigating the causal relationship between sleeplessness and nocturnal worry. A 2 x 2 (Worry x Induced sleeplessness) analysis of covariance design was used. The first factor consisted of a subject variable defined by scoring either high or low on a trait measure of worry (the Penn State Worry Questionnaire) and the second factor consisted of 300 mg caffeine or placebo. A total of 96 female undergraduate students participated. The dependent variables comprised measures of nocturnal worry (the Night-Time Thoughts Questionnaire) and subjective and objective sleep parameters. Overall, caffeine caused an increase in nocturnal worry and sleeplessness. A significant interaction effect occurred between Worry and Induced sleeplessness on one of the objective sleep parameters, but no other interaction effects were significant. The results suggest that worry may occur as an epiphenomenon of sleeplessness.     

Caffeine increases false memory in nonhabitual consumers

Insight into caffeine's equivocal effects on memory can be derived from work suggesting both emotional arousal and psychosocial stress increase false memory rates without increasing veridical memory. This study investigated how a range of caffeine doses affect veridical and false memory formation in nonhabitual consumers. A double-blind, repeated-measures design with caffeine (0 mg, 100 mg, 200 mg, 400 mg caffeine) was used to examine memory using the Deese-Roediger-McDermott (DRM) paradigm. Results showed that caffeine modulated arousal levels, peaking at 200 mg and returning to near baseline levels at 400 mg. Main effects of caffeine demonstrated higher critical lure recall and recognition ratings (i.e., false memory) as a function of dose, again peaking at 200 mg. Those who showed the highest arousal increases as a function of caffeine also tended to produce the highest false recall and recognition rates. Veridical memory was not affected. Results demonstrate that consumption of as little as 100 mg of caffeine elicits reliable inverted-U shape changes in arousal and, in turn, false memories in individuals who do not habitually consume caffeine.