# we cannot compare the follicular phase with the luteal phase > Systematic reviews of menstrual cycle research (e.g., Schmalenberger et al., 2019) show that many studies draw comparisons between the two halves of the cycle (i.e., follicular vs. luteal). However, **many different hormonal events and levels characterize the follicular and the luteal phase of a menstrual cycle**. The influence of a particular hormonal event on the outcome of interest cannot be accurately assessed by these two broad phases, and effects themselves may be washed out by dynamic changes within each phase; thus, this method of coding is not recommended for empirical studies[[(Schmalenberger et al., 2021)#^domi0]]