Lili Reinhart is opening up about her health struggles after a recent diagnosis.

The "Riverdale" star, 27, shared in a TikTok on Monday that she was diagnosed with alopecia "in the midst of a major depressive episode."

Alopecia areata is an autoimmune disorder that causes hair loss. According to the National Alopecia Areata Foundation, about 6.8 million people in the U.S. and 147 million people worldwide have, or will develop, alopecia during their lifetime.

The TikTok showed Reinhart undergoing red light therapy, which according to the Cleveland Clinic uses low-wavelength red light to treat numerous conditions and can be used to improve hair growth. The actress mouthed along to an audio clip that says, "I'm pushed beyond limits of what a person should be pushed to endure."

"Red light therapy is my new best friend," Reinhart wrote in the caption.

Reinhart, who played Betty Cooper on "Riverdale" and is also known for roles in "Hustlers" and "Look Both Ways," has previously been open about her mental health struggles. In a 2021 Instagram story, she said she sometimes feels "really defeated by my depression," an "exhausting battle" that she has been "fighting for 11 years."

"Some days, like today, it can feel intolerable," she wrote at the time. "This is a reminder to my fellow warriors that it's okay to have days where you don't want to fight anymore."

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The actress also discussed battling depression and anxiety on the "Armchair Expert" podcast in 2022.

"I feel that I can handle my depression and my sadness," she said. "It's the anxiety that becomes unbearable. It feels like this engine inside you that's running, and there's nowhere for it to go."

Reinhart's TikTok received numerous comments from fans who praised her for bringing awareness to alopecia and mental health issues.

"I have alopecia and my health and depression make it worse," one comment said. "Sending love."

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Other celebrities who have discussed having alopecia include Neve Campbell and Jada Pinkett Smith, the latter of whom was controversially mocked for her bald head by Chris Rock at the 2022 Oscars before Will Smith slapped him.

"I was in the shower one day, and then just handfuls of hair just in my hands, and I was just like, 'Oh my God, am I going bald?'" Pinkett Smith recalled in a 2018 episode of her show "Red Table Talk."

"It was one of those times in my life where I was literally shaking with fear."

Contributing: Analis Bailey