We already know that in the years leading up to menopause, often called perimenopause, women can experience a lot of symptoms, both physical and mental. But a new study has quantified the risk of depression for perimenopausal women, and the results are shocking: It found that women in this stage of life are around 40% more likely to become depressed.

“Our findings show just how significantly the mental health of perimenopausal women can suffer during this time,” Dr. Aimee Spector, author of the study published in the Journal of Affective Disorders, said in a press release. “We need greater awareness and support to ensure they receive appropriate help and care both medically, in the workplace and at home.”

According to Johns Hopkins, perimenopause typically occurs during the period of about three to five years before menopause, which starts when a woman has gone 12 full months without menstruating. Perimenopause is a transitional phase that happens when the ovaries start to slow down and gradually stop working, and during it, estrogen and progesterone levels can fluctuate, causing irregular menstrual cycles and other symptoms, including mood swings.

Dr. Spector’s study looked at 9,141 women from the United States, Australia, China, the Netherlands, and Switzerland who provided information about their moods, mental health, and interest in doing activities over time. The study authors found the significantly increased risk of depression during perimenopause, but didn’t find a significant risk for depression during premenopause or postmenopause. Experts now say this points to the variability of hormone levels during perimenopause likely playing a role. The study’s authors note that estrogen has been found to affect the metabolism of dopamine, norepinephrine, β-endorphin, and serotonin, which all play a role in mental health.

Given this study’s findings, experts say it’s important for doctors and women in or near perimenopause to be aware of the heightened risk and to watch for symptoms of depression or depressive episodes, especially if they’ve struggled with mood orders at any other point in their lives.

“Depression is a chronic disease that is typically recurrent over the lifetime,” Dr. Rebecca Thurston, Pittsburgh Foundation Chair in Women’s Health and Dementia at the University of Pittsburgh, explained. “We know that these episodes can snowball — if left untreated, they can become increasingly severe. This underscores the importance of not ignoring symptoms and getting them treated.”