You expect to be a teary-eyed mess if you watch Sleepless In Seattle while PMSing, but hormones could also leave you susceptible to other, more surprising psychological side-effects: A new study from University College London finds that women may experience three times as many intrusive thoughts and memories about a stressful event when they’re between days 16 and 20 of their menstrual cycle than if they’re at any other point in it (the day your period starts is considered day one).
Researchers had healthy women between ages 18 and 35 who weren’t on oral contraceptives watch a traumatic video. Then, over the next several days, they asked the women to write down any unwanted thoughts they had in response to the video. Women had significantly more intrusive memories during what’s known as the early luteal phase, which generally falls between days 16 and 20 of the cycle.
“Intrusive thoughts are a natural phenomenon,” says lead researcher Sunjeev Kamboj, PhD, a clinical psychology lecturer at University of College London. While they may be disturbing at times, he doesn’t suggest actively trying to suppress these types of thoughts. “We know that if people are asked to not think of something, they actually think about it more often,” he says. If you find yourself fixating on distressing thoughts for an extended period of time, visit your doctor, who can discuss treatment options with you.
Of course, this effect—and PMS—aren’t the only ways that fluctuations in ovarian hormones can influence your mood. OB/GYN Suzanne Gilberg-Lenz, MD, explains how various points in your cycle may affect you (assuming you’re not on hormonal birth control, which changes your hormonal fluctuations):
When you’ll feel most empathetic
Research indicates that progesterone may inhibit your ability to read others’ emotions through their facial expressions. So around day five or six of your cycle, when progesterone is at a low, Gilberg-Lenz says you may find that you naturally connect better with others.
When you’ll feel sexiest
When your body is getting ready to release an egg—generally between days five and 13 of your cycle—feel-good estrogen spikes. You’ll likely feel super confident, feminine, and sexy in these days just before you’re most fertile, says Gilberg-Lenz.
When you’ll feel most Zen
Estrogen and testosterone suddenly drop around day 16 (although this can occur any time between day five and 22 of your cycle), triggering the release of an egg. At the same time, you’ll experience a rise in progesterone, which Gilberg-Lenz sometimes refers to as “the calming or homebody hormone.” You may feel you need more rest and have some serious cravings during this time, which is likely your body’s way to protect itself should pregnancy occurs, she says.
More from Women’s Health:
Is PMS a Myth?
Fascinating Facts About Your Period
PMS: Make the Most of Menstruation