On June 1, a short, emotional video popped up on TikTok with news about Sarah Mandel, a 42-year-old psychologist, wife and mother of two young daughters.
“If you’re reading these words right now,” the message on the screen said, “then I have died.”
She had asked for help in creating the video while in a weakened state after learning that she had little time left.
“Only a year ago, I never in a million years would have thought I would want my death announced on social media,” she said in the video. But in the previous year she had found encouragement from the comments she received on TikTok after posting videos about the course and treatment of the advanced, metastatic breast cancer she had been diagnosed with in 2017.
And so there she was, delivering the news to the world and a cosmic message to her daughters, Sophie, 10, and Siena, 6.
“I love you and I am so proud of you,” she told them. “I may be somewhere beyond our concepts of infinity. That’s how much I love you.”
Ms. Mandel’s final video, a series of pictures and clips, showed her very much alive: blowing out a candle on a 42nd birthday cupcake; stretching in her hospital room; dancing with her family; looking thrilled after opening a box filled with copies of her newly published book; and singing along with a band in a plaza after leaving a chemotherapy session.
The video was posted on the day she died of the cancer at her home in Manhattan, her husband, Derek Rodenhausen, said.
The video has been seen 1.7 million times.
Sarah Hope Mandel was born on June 28, 1981, in Manhattan. Her mother, Sally (Allen) Mandel, is a novelist, and her father, Barry, is a lawyer.
Ms. Mandel graduated from Bard College in 2003 with a bachelor’s degree in fine and studio arts and contemplated painting and singing as careers. After college, she sang in bars and clubs, including the Bitter End in Greenwich Village, but turned to psychology, a field that intrigued her enough to take courses in it at Bard and do volunteer work. She earned a postgraduate psychology certificate from Columbia University in 2009.
While pursuing a doctorate in psychology at Rutgers University, Ms. Mandel worked as a therapist in New York at Fordham University’s mental health services program, St. Luke’s-Roosevelt Hospital Center and Lincoln Medical Center.
Soon after receiving her degree from Rutgers in 2015, she began work as a licensed clinical psychologist at the Institute for Behavior Therapy in Manhattan.
But in the fall of 2017, while she was in the third trimester of her pregnancy with Siena, Ms. Mandel went to the doctor to have a lump in her right breast examined. Her online research suggested that it might be a clogged milk duct; her obstetrician concurred, but sent her for a sonogram, which found that the lump was suspicious.
A biopsy showed that it was Stage 4 breast cancer and that it had spread to her liver and bones. After three months of treatment, though, she received remarkable news: A PET scan found no sign of cancer in her body, a nearly miraculous outcome. The result was so overwhelming that it left her in a traumatized, dissociated state.
“I felt guilty because I felt nothing,” she said on the podcast “Moms Don’t Have Time to Read Books” in 2023. “Here there were so many other women with this disease who would just do anything to get this kind of response. I felt nothing. What a betrayal to these women.”
She was unable to deal with her devastation until she applied a technique — narrative therapy — that she had employed with clients who suffered from traumas. She guided them to dig deeply into their traumatic memories, piece together even the most upsetting details, then write them down and read them aloud in therapy sessions.
“I started to write. The words just tumbled out onto the page,” she said on the podcast. Soon she had what she referred to as her “trauma narrative,” which she read to her husband before expanding it into “Little Earthquakes: A Memoir.” The book was published in 2023 — two years after the cancer had erupted from a dormant state in her brain, causing her to give up her psychology practice. The cancer spread to her cerebral spinal fluid in 2023.
“Writing became medicine to help me cope with the uncertainty of the here and now,” she wrote in “Little Earthquakes.” “And perhaps the biggest surprise of all is that through the writing of my trauma narrative emerged my love letter to life.”
In its review, Publishers Weekly wrote that Ms. Mandel “nimbly portrays the cocktail of emotions unearthed by the sentence ‘You’ve got cancer,’ and paints her supportive family with staggering compassion. Her dogged fight for her life will awe readers.”
In addition to her husband and parents, Ms. Mandel is survived by her daughters and her brother, Benjamin.
Ms. Mandel had not told anyone in her family about her plan to announce her death on TikTok. She had worked with Micaela Williams on social media marketing for her book, and in March she asked Ms. Williams to work on the final video. Ms. Williams laid Ms. Mandel’s messages over pictures and video clips.
“She did approve of the final post before she passed,” Ms. Williams said in an email.
When Ms. Mandel died, Mr. Rodenhausen notified everyone on a list of people she had given him. After Ms. Williams received the email, she posted the video.
“I didn’t see the video for probably at least 24 hours or so after it went up,” Mr. Rodenhausen said in an email. He added, “I’ve actually never been a user of TikTok myself, so I set up an account so I could see it.”