The Mayo Clinic reports that 75 to 85 percent of women experience hot flashes during perimenopause.

CNN: Navigating the ups and downs of perimenopause

You'll know it's perimenopause if you also experience occasional hot flashes, sleep trouble, anxiety, and mood changes, Goldberg said.

CNN: Your period: What's normal, what's not, what to do

Becker offers comfort and support to her patients by reassuring them that the symptoms are common among women going through perimenopause.

CNN: Navigating the ups and downs of perimenopause

If it's not perimenopause, it could be stress, severe weight loss, or extreme weight gain, all of which can knock your hormones out of whack.

CNN: Your period: What's normal, what's not, what to do

Most of the study participants had been diagnosed with anxiety disorder or depression, but some were experiencing anxiety stemming from a health condition, such as surgery or perimenopause.

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"For those women who are exercising, who are eating well, who are really happy in their work and relationships, they may go through perimenopause and never ever notice it, " Northrup said.

CNN: Navigating the ups and downs of perimenopause

Irregular periods -- maybe yours used to come every 28 days but is now arriving on day 21, 35, 28, and back to 21 again -- can be a symptom of perimenopause.

CNN: Your period: What's normal, what's not, what to do