Mrs. Richardson, whose body was found by family members on Monday, apparently died in her sleep sometime during the weekend, her stepson Kevin Richardson said.
A former Roman Catholic nun, Mrs. Richardson left her order in 1966, a journey she recounted in a memoir, “The Buried Life,” published in 1971. In secular life, she became a member of New York’s social set, and was married for three decades to Ham Richardson, a tennis star who later ran his own investment concern, with homes on Park Avenue and in Bridgehampton, on Long Island.
At Seventeen, which she edited from 1975 until her retirement in 1993, Mrs. Richardson was known for introducing frank discussions of delicate subjects — including sex, anorexia and suicide — from which the magazine, aimed at teenage girls and long considered a bastion of wholesomeness, had traditionally shied away.
Under Mrs. Richardson’s stewardship, certain aspects of the magazine remained comfortably familiar. “Secrets of Staying Thin,” promised one cover, from 1980; “Those Dreamy Summer Romances,” proclaimed another that year.
But other cover lines betrayed her resolve to address modern readers’ concerns: “Teen Suicide: The Danger Signals,” “What You Must Know About Herpes.”
In 1982, Mrs. Richardson instituted a regular column, “Sex and Your Body,” which explored subjects like gynecological health, sexual relations and birth control.
“We’ve been talking about it for years and trying to figure out how to go at it in a tasteful manner,” she told The Chicago Tribune in 1983. “We don’t want to be frightening to a young girl, or permissive. But the demands of the time finally brought us around to it.”
All this was a far cry from her life as Sister Agnes Marie, and from the quiet routine of her days in the convent, where she had lived from the ages of 18 to 36.
Agnes Theresa Turk, known as Midge because of her petite stature, was born in Los Angeles on March 26, 1930, the youngest daughter of a Roman Catholic family. As a girl, she worked as an extra in more than a hundred Hollywood films, sometimes appearing opposite Shirley Temple.
At 18, wanting a life of service, she forsook her lively home, her active social life and her boyfriend to enter the Sisters of the Immaculate Heart of Mary, a teaching order with a motherhouse in the Hollywood hills.
Sister Agnes Marie, as she was known in religion, earned bachelor’s and master’s degrees from Immaculate Heart College, run by her order. She embarked on a career as an educator, teaching English, French and drama in local parochial schools and later becoming the principal of a Catholic high school in a blighted, largely Latino section of Los Angeles.
She loved the life, but by the mid-1960s she had become depressed and exhausted — frustrated, she wrote, by what she saw as the failure of diocesan hierarchy to meet the needs of the impoverished community she served. She suffered two bouts of temporary blindness, brought on, her doctors told her, by strain.
In 1966, after much soul-searching, Sister Agnes Marie asked to be released from her vows. (In 1970, Anita Caspary, the mother superior of the Sisters of the Immaculate Heart, led an exodus of 300 nuns from the order in response to what they described as the failure of the diocese to lift outmoded restrictions on nuns’ lives.)
At 36, Agnes Turk found herself on her own for the first time. Carrying a single suitcase, she made for New York: it was one place, she reasoned, that offered career opportunities for women. She found a job as an assistant to a dean at New York University, sleeping on the floor of her tiny Greenwich Village apartment because she could not afford furniture.
She learned to navigate an alien social world. Once, preparing for a date, she washed her hair only to realize she did not own a hair dryer. She stuck her head pragmatically in the oven, emerging with singed hair.
After working as the college editor of Glamour magazine and at Scholastic Publications, she joined Seventeen as executive editor, becoming editor in chief in 1985.
Mrs. Richardson’s husband, whom she married in 1974, died in 2006. The No. 1-ranked tennis player in the United States in 1956 and 1958, he won 17 national titles and played on seven Davis Cup teams.
Besides her stepson Kevin, survivors include another stepson, Ken Richardson; a stepdaughter, Kit Sawers; two sisters, Gwendolyn Tighe and Marie Smith; and five step-grandchildren.
Mrs. Richardson was also the author of a children’s biography of a friend, the photographer Gordon Parks.
In an interview with The New York Times in 1970, she described the forces that led her first to take the veil and later to relinquish it:
“I entered the convent not so much because I believed in the church as that I believed in helping people,” she said. “I’d never had any great thing about dressing up in those clothes and jangling my rosary beads.”
