Betty Ford said yesterday she is addicted to alcohol as well as to the medication that led to her treatment at Long Beach Naval Hospital.

Mrs. Ford, the 60-year-old wife of former President Ford, was admitted to the California hospital's alcohol and drug abuse center 12 days ago. "I have found I am not only addicted to the medication I have been taking for my arthritis but also to alcohol," Mrs. Ford said in a statement read at the hospital by a family spokesman.

Neither Mrs. Ford nor her husband, who was in the hospital at the time of the press briefing, attended the news conference.

Dr. Joseph Pursch, head of the center, said Mrs. Ford would be given carefully controlled drugs for her arthritis and that she would not drink alcohol in the future. He declined to describe the specific treatment she is undergoing.

"This program is well known throughout the country," said Mrs. Ford in the statement, "and I am pleased to have the opportunity to attend it. I expect this treatment and fellowship to be a solution for my problems. I embrace it, not only for me, but all the many others who are here to participate."

The admission last week by Mrs. Ford of her medication problems came after several years of speculation by friends and members of the press who had observed her slurerd speech on several occasions.

At the briefing yesterday, Ford spokesman Bob Barrett declined to answer questions about the measure of Mrs. Ford's drinking or how long it had been a problem.

He said he felt Mrs. Ford's statements had gone to the necessary "point of candor" at this time, and predicted Mrs. Ford would speak out on the subject herself later.

The statement yesterday came as a surprise to several of Mrs. Ford's close friends and staff, who recall her as a social drinker. These sources said if she had any drinking problem when she lived in the White House, they were not aware of it.

'Through the 13 years I have known her, I have seen her drink at parties but I never saw her overdrink," said one friend. "I had lunch at the White House with her several times and drinks weren't even offered," said another Washington friend.

Others said Mrs. Ford drank vodka and tonic during her White House years but "never more than a couple.

Mrs. Ford took medications to ease the often excruciating pain of arthritis in her neck and muscle spasms that have bothered her for years.On two occasions, while she was in the White House, Mrs. Ford told reporters she was taking Valium, the most commonly prescribed tranquillizer and muscle relaxant. Doctors at Long Beach Naval Hospital would not list the name of drugs when Mrs. Ford was admitted last week.

At that time, Mrs. Ford said, "I was overmedicating myself. It's an insidious thing and I needed to rid myself of its damaging effects.

Mrs. Ford was facing a time of stress - moving into a new home, meeting a book deadline, coping with her husband's frequent absences because of a heavy schedule of lectures, dinners and golf tournaments - when she entered the hospital last week.

"She was generally overwrought - there was a surfaciang of a lot of things," said one family aide yesterday.

However, both the aide and several other friends say her decision to confront the problem had been reached two weeks earlier after a family council. There was no particular crisis, the sources say, but more of a realization by Mrs. Ford and her family that her problem was a serious one.

Mrs. Ford's candor after her operation for breast cancer in 1974 Prompted thousands of women to seek frequent checkups and examinations. Experts in the field of drug abuse hailed her similar candor yesterday.

"I believe the nation is going to go through a major change because of this. Mrs. Ford has made a big contribution - there are hundreds of thousand of other Americans who need this rehabilitation," said Dr. Robert DuPont, director of the Department of Health, Education and Welfare's National Institute of the Drug Abuse (NIDA).

Mrs. Ford's case is fairly typical," he said. "Of a recent study of 15 drug abuse centers targeting the use of prescription drugs, some 40 percent who had problems with Valium had problems with alcohol."

"The effect of one drink is greater if mixed with medication, "said a spokesman for the National Institute of Alcoholism and Alcohol Abuse. "The degree of impairment of taking alcohol and medication at the same time is almost always not apparent to the drinker."

Steve Ford has said "my mother does drink, just as many other Poeple do in this country. There always seems to be a Problem mixing alcohol with drugs." He said he was confident she could solve her latest problems.

"The Good Lord seems to keep challenging her witg tasks, and she hasn't failed yet."