Hey ladies: Want to know the reason behind bloating, bad moods, and chocolate cravings right before Aunt Flow comes to town? A new study suggests women’s experience of PMS symptoms depends on their sensitivity to allopregnanolone, a hormone that occurs naturally in the body during ovulation and pregnancy.

To test reactions to allopregnanolone, scientists administered large doses of the hormone (as much as pregnant women usually release) to 10 non-pregnant women. They then measured women’s response to the hormone before and after their menstrual cycles.

Turns out ladies who suffer from severe PMS are more sensitive to allopregnanolone before their period than those who don’t get moody. Researchers suggest this finding means people adapt to hormonal changes differently (meaning some are more likely to snap at boyfriends and accidentally cry during commercials than others).

Scientists have yet to figure out what causes this hormonal difference, but they propose it depends on variations in the GABA system, which regulates a neurotransmitter that circulates during ovulation.

But remember: This study tested just 10 women, which makes it hard to apply the findings to the general population. So before giving up on Midol, know the research isn’t conclusive, and there are natural ways to help fight those pre-period blues. Drink plenty of water, exercise, and try to avoid alcohol and other simple sugars. (And perhaps give into that chocolate craving, too.)