Camila Mendes has teamed up with a nonprofit organization to raise awareness for illnesses that affect so many in devastating ways, and for her, it's personal: She wants to end stigmas attached to eating disorders, and her involvement in the cause is rooted in her own experiences.

The Riverdale star shared that she's working with Project HEAL before an October 21 event with the organization, and she explained how witnessing her sister's battle with an eating disorder — and suffering symptoms herself — inspired her to get involved.

"I can say from experience that eating disorders are serious mental illnesses," she wrote. "Growing up, I watched my big sister suffer from one for many years, and I've experienced periods of my life when I've suffered symptoms as well."

For more information on Project HEAL, click here.