Entertainment TV Kristen Johnston Mourns Sister Who 'Lost Her Battle with Addiction': 'She's Finally at Peace' "She had the best belly laugh in the world," said the 3rd Rock from the Sun actress, who's been open about her own battle with addiction By Benjamin VanHoose Benjamin VanHoose Twitter Benjamin VanHoose is an Associate Editor on the Movies team at PEOPLE. He's worked at PEOPLE for over three years as a writer and reporter across our Entertainment, Lifestyle and News teams, covering everything from the Johnny Depp v. Amber Heard trial to the Oscars. He regularly covers red carpet events and has interviewed stars like Drew Barrymore, Ryan Reynolds and Kirsten Dunst. He previously worked as a copy editor at Topix Media Lab. People Editorial Guidelines Published on August 18, 2020 10:28 AM Share Tweet Pin Email Kristen Johnston. Photo: Dave Kotinsky/Getty Images Kristen Johnston is mourning the loss of her sister after a battle with addiction. On Tuesday, the 3rd Rock from the Sun star, 52, shared on Twitter that her younger sister, Julie, died on Monday. Johnston remembered her sibling with a sunny throwback photograph of the two of them smiling together. "Yesterday my beautiful younger sister Julie lost her battle with addiction. 💔 I know she’s finally at peace. She had the best belly laugh in the world," wrote the Mom actress. Johnston has previously been open about her own past drug and alcohol abuse, detailing her addiction recovery in her 2012 memoir, Guts: The Endless Follies and Tiny Triumphs of a Giant Disaster. Promoting her emotional book back in 2012, Johnston opened up to Entertainment Weekly about battling addiction, telling the outlet that it's a day-by-day process. "The most important thing I want to express to people is that I’m not cured. I could probably relapse in a minute. Who knows?" she said at the time. "It’s just a weird disease that sneaks up on you and all of a sudden you’re boozing at the bar, or whatever. And it doesn’t have to be because of you or pressure or this-or-that. It just can be." She added: "The most important thing is that I didn’t want to set myself up for failure and be like, 'Look at me!' I wanted to write the book that I needed when I was suffering." 'There Was a Lot of Pain': 23 Stars on Their Experiences with Addiction Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories In a July 2013 op-ed for The New York Times, Johnston explained the harmful stigmas surrounding addiction and the shame placed on people who suffer from the disease. The actress wrote that "we're not a joke anymore." "It’s time for addiction to stand up and demand some respect. Because every time someone is ostracized for being an addict, every time there’s a breathless, trumped-up, sensational headline, every time we giggle at a wasted celebrity, and every time addiction is televised as salacious entertainment, yet another addict is shamed into silence," wrote Johnston. The actress was also diagnosed with lupus myelitis, a rare form of lupus that affects the spinal cord. Johnston told PEOPLE in 2014 about her health battle: “Every single day is a gift, and I don’t take one second of it for granted.” If you or someone you know is struggling with addiction, please contact the SAMHSA substance abuse helpline at 1-800-662-HELP.