Quick: Think of someone snoozing and snoring.

Did you imagine a guy? Men are more likely to snore than women, and they also have less trouble falling asleep. The Cut spoke with sleep experts to find out the scientific reasons for this sleep disparity between the sexes. Here are three reasons women may spend more time counting sheep than men:

1. Hormones

Estrogen fluctuates throughout your menstrual cycle, and research shows it can affect your circadian rhythm.Estrogen receptor 1 modulates circadian rhythms in adult female mice. Blattner MS, Mahoney MM. Chronobiology international, 2014, Feb.;31(5):1525-6073.

2. Periods

Speaking of menstrual cycles, periods come with oh-so fun side effects, like cramping and bloating, that make it harder to sleep.

3. Pregnancy

Growing a tiny human is downright exhausting—and you’d think that would make it easier to fall asleep. But pregnant women are more likely to have obstructive sleep apnea and Restless Legs Syndrome, making the sleep they do get less restful.

Check out the full story for the full list of factors, including stress, anxiety, and depression, that affect women’s sleep habits.