Hair loss may seem like a guy thing, but women can be severely affected by thinning hair, too. In fact, about 21 million women in the U.S. have experienced hair loss, according to the International Society of Hair Restoration, and 80% of women have noticeable hair loss by age 60 (compared with 65% of men).

“Female hair loss is grossly underestimated,” says Suneel Chilukuri, M.D., a cosmetic dermatologist and the founder of Refresh Dermatology in Houston. While genetics or certain illnesses may lead to thinning hair, your diet, lifestyle, and even how you wear your hair can play a part.

“Hair loss is multifactorial, but it’s highly dependent on your environment and other factors like stress, inflammation, and hormones,” says Sophia Kogan, M.D., the chief medical officer at Nutrafol, a hair-growth supplements company. Today, she says, more women are noticing changes in their locks and at ever-younger ages, with some seeing hair loss in their 20s or 30s. Here’s what may be causing the damage—and what you can do to help before it gets worse.