Patti Davis says she isn't the only Reagan who said yes to drugs. In her just-published autobiography, she writes that her mother, Nancy Reagan, habitually used prescription tranquilizers, sleeping pills and diuretics even after she and Ronald Reagan moved to the White House. She also writes that her mother often slapped her when she was growing up.

Davis, 39, stops short of using the word "addict" to describe the former First Lady, who during her husband's two terms as president exhorted millions of Americans to "Just Say No" to drugs. However, she says that for long periods her mother was taking tranquilizers three to four times a day. "I didn't want to call her an addict -- I'm not a doctor and that sounds like a medical diagnosis to me," Davis said in an interview this week on the eve of a national book tour to publicize "The Way I See It," published by G.P. Putnam's Sons.

"I was definitely an addict. I would say she was dependent," said Davis. But later, describing her mother as part of "the Miltown generation, going up the ladder of tranquilizers that were in vogue," she said, "We were both pill addicts."

In a statement released yesterday, the Reagans said: "We are saddened and pained by stories in the most recent book by our daughter, Patti Davis. It contains many hurtful and shocking claims including charges of physical mistreatment and substance abuse which, for the record, are absolutely false. We have always loved Patti and hope the day will come when she rejoins the family. Toward that end, we see no useful purpose for further comment."

Davis says that at various times she stole Miltown, Librium, Valium and Quaaludes -- all tranquilizers -- from her mother's bathroom, trading them for the amphetamines she got from friends in exchange. If Mrs. Reagan figured it out, Davis says she never confronted her about it. Once, Davis writes, having found "black beauties," a potent street drug, in her daughter's room, Mrs. Reagan left it to her husband to ask the questions.

"She didn't say, 'How many have you taken? How long have you been taking them? Is that why you're so thin?' " Davis recalled this week. "I think that was the moment when I thought, 'This woman and I know each other very well.' I don't think my mother realizes that I was addicted. It would probably be too close to her own situation, so I don't think she would want to consider that. I've heard her say, 'My kids have experimented with grass,' and I think she really believes that because she wants to."

Writing that "In our use of pills, we had converged," Davis theorizes that "even though we chose opposite drugs, even though we didn't admit to addiction, we shared a common secret."

Davis has already told a number of Reagan family secrets in three thinly veiled semi-autobiographical novels that came out during the 1980s. This book, however, puts Reagan names and faces to her by-now-familiar Angry Mother and Distant Father characters. Of Mrs. Reagan, Davis writes that her "violence made me fear her, and fear that she may have passed along that rage to me in the mysterious linkage of chromosomes." Of her father, she writes that "his presence felt like absence."

She tells that she was continuously accused of lying by her parents and grandparents, who refused to believe that her mother slapped her. And she says her father never witnessed that abuse, but her brother Ron did. She writes that he told her, "I used to look in your room and see her slapping you, and I remember thinking that I was never going to let that happen to me." A spokesman for Ron Reagan said yesterday that he was not commenting on his sister's assertions.

Holmes Tuttle, one of Reagan's "Kitchen Cabinet" advisers, also witnessed Nancy Reagan's violence, according to the book. Davis writes that after her mother attacked her in his presence, Tuttle "jumped up and pulled her off me," telling Mrs. Reagan never to do that in front of him again. "I don't think he ever said anything to my father about that incident; if he did, my father never mentioned it, which wouldn't have been unusual either."

Tuttle died in 1989.

Her assertion that her mother habitually took prescription drugs brought disbelief yesterday from friends of the Reagans, among them Charles Z. Wick, director of the U.S. Information Agency in the Reagan years, who has known the family since the children were in grammar school.

"Nancy won't even take a drink," said Wick. "She's always been very careful about her body. It would be foreign to her whole outlook. Unfortunately Patti has to be very, very sick. They love her. They can't believe she would do this kind of thing. It's one thing to tell 'family secrets,' but to make up something so totally untrue for $500,000 {the reported advance for this book} is a shock to them. They recognize she must be sick, but what can they do?"

Wendy Weber, Davis's roommate at the University of Southern California in 1972-73, who later worked on Mrs. Reagan's staff at the White House, said this week, "In some ways Patti was her own worst enemy. I worried about her. Her parents worried about her. She refused to take their help. I went to talk to her therapist. I didn't know if she was suicidal."

Davis, in fact, says she did contemplate suicide while she was a student at Northwestern University, before she entered USC. In the book, she describes going into the bathroom, locking the door and taking a single-edge razor blade from the medicine cabinet and touching it to her wrist.

She writes that she "felt how easy it would be -- not much pressure, even, the skin's so thin there. Just a quick movement -- that's all it would take. I'd heard you just get sleepy as the blood drains out, that it was not that painful. I think I sat there for nearly an hour, imagining my death."

Among other revelations certain to provide grist for renewed speculation about the Reagan presidency is her description of Inauguration Day 1981. Davis writes that as the family waited to walk onto the platform for Reagan's swearing-in, "someone (I think it was Ed Meese, but I could be confused about that because several men run together in my mind and become faceless) came up to my father and said, 'The hostages have just lifted off.' My father closed his eyes and said, 'Thank God,' almost under his breath. Then he said to my mother, 'They've just left Iran.' "

Later, as Reagan began his inaugural address, Davis says, she "naively" expected him to announce "that the hostages had just left Iran. It was only then, when he didn't, that the significance of what I'd witnessed hit me. Of course he couldn't announce that. He wasn't supposed to know about it yet. He wasn't yet president when he got the news."

Davis writes that at the post-inaugural luncheon where Reagan announced that the hostages had been released, she heard her mother telling someone, "Well, you know why this happened. They were afraid of Ronnie. They knew he'd take action and not be meek like Carter." Davis adds that she doesn't think the release had anything to do with fear. "It had to do with a deal, struck before the deal-maker was in office." She offers no corroboration for this assertion.

(In his 1987 book, "Behind the Scenes," former Reagan aide Michael K. Deaver writes that 20 minutes after Reagan was sworn in, the news that Iran had released the hostages reached him at the luncheon and he passed a note to Reagan, who then stood up and made the announcement.)

But the stunning news, and what Davis said this week she "agonized a lot" about in writing the book is the disclosure of her mother's drug "dependency." Kitty Kelley raised the possibility last year in her unauthorized biography, "Nancy Reagan," quoting an unidentified "senior staff" aide to the former First Lady as saying, "I wondered if she was on some kind of medication. She always had so much energy that I thought maybe she was on amphetamines to curb her appetite."

This week Davis said that she recognized many of the stories in Kelley's book and that some of them were true. As she tells it, she remembered closing Kelley's book and saying, " 'This is never going to end, this perception of my family, until somebody tells the truth.' "

She thinks people will have compassion for Nancy Reagan. "She has been judged as a hypocrite pretty much across the board in her involvement in the drug issue," said Davis. Citing in particular the public relations effort that launched Mrs. Reagan's anti-drug campaign in 1982 and more recently her withdrawal of support from the drug program Phoenix House, Davis said she nonetheless never thought her mother was hypocritical. "I knew the truth underneath that. I knew that this was someone with a problem. And the truth was that her choice of that issue was both an act of denial and a cry for help."

So in writing a book that she says lays everything out -- lies surrounding her own birth seven months after her parents were married, her decision to be sterilized to prevent passing along Nancy Reagan's genes to another generation (a procedure she says she later underwent surgery to reverse), her romantic affairs and promiscuous lifestyle with such partners as Eagles star Bernie Leadon, Dennis Wilson of the Beach Boys, actors Timothy Hutton, Peter Strauss and Kris Kristofferson -- she said she "committed the cardinal sin in this family. I decided to tell the truth. I've rejected the basic ethic of this family, which is never let people know who you are."

Davis thinks that young Anne Robbins, Mrs. Reagan's name at birth, suffered emotional abuse at the hands of her mother and stepfather. "To string a child along for 10 years as my grandfather {Chicago neurosurgeon Loyal Davis} did, saying, 'Well, maybe I'll give you my name if you earn my love,' that child is going to grow up feeling totally insecure and unworthy of love, with no concept of unconditional love or truth."

That, Davis said, was probably "key to my way of thinking, bringing me to a point of forgiving my parents. If all they got was one language and one way of thinking, of course that's what they're going to teach me."