Stress and medical conditions increase women’s risk of hair loss, according to a new study.

In the past, alopecia in women was thought to be largely related to genetics and hormones, but the new research adds increased stress, smoking, having more children, and a history of hypertension and cancer to the list of alopecia causes in women.

The study, which appears in the December issue of Plastic and Reconstructive Surgery, sheds light on possible ways to prevent hair loss in women.

Researchers led by Bahman Guyuron, MD, of Case Western Reserve University School of Medicine in Cleveland, analyzed risk factors for hair thinning in a series of 98 identical female twins with an average age of 54. The twins posed for standard photographs, which the researchers used to measure hair loss or thinning at the front, sides, and top of the head. Testosterone levels were measured.

Participants also completed detailed questionnaires assessing a wide range of possible environmental, lifestyle, and health-related factors. Higher testosterone levels were associated with increased hair loss, particularly at the sides and top of the head, but women reporting higher levels of stress had more hair loss and thinning than their counterparts with lower stress levels. Life situations related to higher stress–including being separated or divorced, multiple marriages and more children–were also linked to hair loss in women, the study showed.

Other risk factors potentially related to high stress levels included higher income. Prolonged sleep was another risk factor, possibly related to depression/anxiety as well as stress.

Several medical risk factors including cancer, high blood pressure, and diabetes were also linked to hair loss risk in women. Smoking, not exercising, and not using sun protection also increased this risk.

Women with higher caffeine intake were actually at lower risk of alopecia, possibly because caffeine counters the hormonal effects leading to hair loss.

“Many of the environmental factors discussed in this study such as smoking, sun exposure, and excessive stress can be targeted by both patients and physicians as potential ways to augment hair loss prevention strategies,” the researchers conclude.