If you've ever lived with multiple people who have periods, you've probably experienced period syncing. Period syncing describes a popular belief that women who live together or spend a lot of time together will see the timing of their monthly periods syncing up or aligning. Roommates, close friends, coworkers, same-sex couples, and family members who start their period on or about the same day every month can feel like this is a special bond between them. But is this a real phenomenon, or just a popular myth?
Curious? Check out this gallery to discover what research has to say about period syncing.