It was in the early 1970s, while her own sons were growing up, that Marie Winn first noticed the change.

Children didn't seem to play anymore. They didn't act, talk or even look like kids anymore. "Eight and 9-year-olds were so savvy, so grown up."

They talked about drugs, sex, divorce, rape.

It was the end of childhood innocence that Winn had noticed. She wanted to delve deeper. Was it just the urban New York kids she knew who were so precocious? Was TV the cause? Parents? Divorce?

Winn spent months interviewing several hundred parents and fourth through sixth-graders ("the heart of childhood") in an effort to look at rural and western children as well as urban families she knew in New York City.

"I found the same behavior and patterns everywhere. An incredibly high level of precocity, and adultification of kids. The carefree years have disappeared."

Cause? "A confluence of many, many circumstances," says Winn, who despite her despair at times over sorting them out has put her unsettling and controversial observations together in the book, Children Without Childhood (Pantheon, 224 pages, $13.95).

"There is a circular effect, everything seems tied to everything else in an extremely complex way. No one cause alone is to blame."

One conclusion: "The greater search for personal fulfillment on the part of adults has led to all sorts of problems for their children. Parents pursue their own goals now, and don't differentiate between what's good for them and good for their kids.

"One crucial example is the divorce epidemic, a root cause of loss of childhood for millions of kids." She devotes a chapter in her book to reviving the idea that it might be better for unhappily married parents to stay together for the sake of the kids. Citing a California study of children of divorce, she says "many marriages that had been unhappy for the adults had been reasonably comfortable, even gratifying, for the children."

Parents may be happier divorced, she concedes, but "their children are pushed prematurely into independence, deprived of their childhood."

Television also is enormously important "in bringing adult scenes into children's lives" far too early, maintains Winn, who detailed TV's overwhelming influence in an earlier book. "But blaming television alone is not quite right either. There are just too many other factors."

Winn, who emphasizes that she is a feminist, wrote her book "to sensitize parents, to make them aware of what they are doing, what the pitfalls are." She would not want to go back to the "old system, because it was unfair to women. Yet children are suffering this way."

Winn perceives the adultification of kids as shrinking parental responsibility. "Childlikeness used to trigger strong protective feelings on the part of parents. Now that kids appear so sophisticated, parents are much more likely to overlook their developmental needs."

However, she adds, "I am very sympathetic to parents because this is a terrible time to be raising kids. If parents' own lives and jobs have gone haywire, it is even harder."

So far as contemporary books for children, "The trends," says Winn, "are depressing. Kids' books feature rape, abortion, child-molestation, incest. Some children do in fact face this, but not all children have to have life's burdens thrust on them. As adults we should be working to prevent these problems, not to expose our kids to them."

Movies? "I am shocked to see that kids go to R-rated movies, often with their whole families. These movies are damaging to young children, with their sadism and explicit sex. Nowadays there is often the feeling that it might be better for kids to know these things. This is new as a way of raising children."

The current tendency to be totally honest, Winn believes, "jeopardizes kids' sense of security."

Winn's own background is both traditional and traumatic. Her psychiatrist father and her mother fled Czechoslovakia "on the last boat" in 1939 to escape the Nazis. She was 3 when they settled in New York.

Married for over 20 years to a New York filmmaker, Winn has two sons in college, one at Harvard and the other studying violin at the University of Indiana. Her sister is New Yorker writer Janet Malcolm.

Winn considers herself lucky because as a free-lance writer she was able to be at home when her sons were young. "Obviously," she concedes, "this is not the answer for most people."

As for answers, Winn is skeptical of "experts." "They foster insecurity," she claims, citing Dr. Spock as the exception. "He said you know more than you think you do. But many other books make parents feel very bad."

Winn readily acknowledges that she has her share of detractors. "There are those who genuinely feel that kids are in fact better off now, people who feel deeply resentful of what they call overprotectiveness of children."

She counters: "One can strive to make childhood less burdensome to children. After all, it isn't kids who will save the world from a nuclear holocaust, it is us."