Moderation of Caffeine's Cognitive Effects by Menstrual Cycle Phase

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Overall, the main purpose of this project is to examine how caffeine affects brain activity and, therefore, behavior across the course of the menstrual cycle. The reasons for doing so are threefold. Firstly, brain activity and performance on tasks changes across the menstrual cycle. Secondly, caffeine also changes brain activity and performance on tasks through its stimulating effects, or its ability to make us perk up'. We don't know, however, if the effects of caffeine on the brain work to alter (for better or worse) some of the changes in brain activity we see across the menstrual cycle, despite the fact that about 88% of the Canadian population regularly consumes caffeine. Finally, and perhaps most importantly, one of the reasons why we don't know how caffeine affects the brain at different points of the menstrual cycle is because in drug studies, women have historically been ignored as participants. This is true of studies looking at recreational drugs, studies looking at medical drugs (such as those to treat HIV or cancer), and studies looking at common drugs like caffeine and nicotine. One major reason why women have been excluded from this type of research is because of the possibility (if not likelihood) that the effects of the drug will change depending on the menstrual cycle phase and it is time consuming and expensive to test women across these different phases. As such, many of these studies have only tested and reported the effects of drugs on men. This is problematic because the results are often generalized to humans as a whole, despite the fact that we often only have data on men, or when we do have data on women either menstrual phase isn't accounted for or only one phase is tested. This is certainly true of caffeine; not only is there very little research looking at how caffeine affects the brain, there is virtually no research examining how these effects change in women across their cycle. Therefore, one major goal of this project is to fill this gap in the literature. Beyond this, we hope this will be the beginning of a program of research in our lab to document the effects of psychoactive substances on the brain across the menstrual cycle to make it easier for women to be included in future studies. This project will be conducted in women who are naturally-cycling', which is to say their menstrual cycle is not affected by hormones from medications, in the menstrual, follicular and luteal phases of their cycle. However, given the popularity of hormone-based birth control (such as the birth control pill), we will also perform these tests in women currently using a hormonal birth control method. At the end of the project, we hope to not only better understand how caffeine affects the way our brains work, but to also begin our understanding of how the menstrual cycle and drugs like caffeine work together to affect or brain's ability to function.