Betty Ford is suffering from the effects of overdependency on a combinations of tranquilizing and painkilling drugs, a common and often tragic conditions among women, medical sources said yesterday.

"This is one of the major health problems of American women - there's a terrible epidemic of overuse of legal and prescription drugs," said the author of a new federally financed report on the prblem.

A physician acquainted with Ford's case told The Washington Post that she has been taking a tranquilizer and a painkiller to combat the often excruiating pain of the arthritis and muscle spasms that have bothered her for years.

He would not name the drugs. But he said any of a commonly used list could have caused her to enter Long Beach Naval Hospital with the admission that "I was over-medicating myself. It's a insidious thing, and I needed to rid myself of its damaging effects."

She recently told a magazine interviewer that she also took a drink sometimes to relax. Even in the amounts often considered to be "social drinking," alcohol can severely aggravate the effects of mood-affecting, muscle -relaxing or pain-easing medicines.

The most commonly used tranquilizer, Valium, may be prescribed either as a muscle relaxant or a tranquilizer.

"What we have in the United States today is indiscriminate overprescribing and overuse of legal and prescription drugs among women," said Muriel Nellis, president of National Research and Communication Associates.

She is principal author of "Drugs, Alcohol and Women's Health," a report compiled for the National Institute on Drug Abuse of the Department of Health, Education and Welfare. The report was based on a nationwide study that she coordinated.

Overuse of painkillers, tranquilizers or alcohol, singly or in combination, can lead to severe emotional problems, nervous symptoms resembling epilepsy and death, "which is often mistakenly labeled as 'suicide.'" Nellis said.

"Mrs. Ford's illness pinpoints this major health dilemna," she said. "We owe her great things for the courage of coming out and admitting this problem, just as she courageously told of her breast cancer in 1974."

When she was First Lady, Ford often told the toll taken on her body and emotions by her chronic neck pain and muscle spasms caused by arthritis and associated connective tissue irritability. She told one interviewer, "Unless you had it, you can't imagine the pain. It radiates all down my left arm, leg and side."

At one point, a doctor who thought part of her trouble might be emotional tension referred her to a psychiatrist. But much of her care over the years was drug care.

In recent weeks friends said she was "harder and harder to live with," another source said yesterday. But a doctor who knows her said, "She got over her breast cancer, and I'm sure she will be saying soon what she has done about this problem. I admire her for accepting it."