You may already pencil in a monthly warning on the calendar to take it easy right before your period, but new research indicates that there’s another “that time of the month” that you should know about. In a University College London study, compared to women at other phases of their cycles, women who were exposed to emotional stressors in the early luteal phase—16 to 20 days after the start of their last period—had three times as many disturbing memories in the days that followed.

READ MORE: How to Deal with Mid-Cycle Stress