Six to 8 percent of psychiatrists and psychologists have sexual relations with their patients even though the practice is unethical and illegal, the American Psychological Association was told this week.

Psychologist Jacqueline Bouhoutsos, who headed the study group at a clinic in Santa Monica, Calif., said that although the percentage is "relatively small," the psychological damage done to patients is apparently very high.

She said reports from therapists indicate that up to 90 percent of the patients involved developed strong fears or distrust of men or therapists, and 11 percent had to be hospitalized. One percent committed suicide.

Bouhoutsos said it is likely that other professions in which there is long, close contact between professionals and clients--such as medicine and social work--have similar rates of unethical sexual intimacy.

The problem of sex in therapy is only now being recognized as serious by the public and the profession, and several new studies are examining the problem from the point of view of both therapist and patient.

Some therapists during the 1970s advocated sex as a possible part of therapy, one expert in the subject said, "but now advocates are extremely rare. There has been a complete retrenchment."

Even though some patients may feel guilty and partly responsible for the incidents of sex, Bouhoutsos said, "the matter is purely the responsiblity of the psychologist or mental health professional."

"Therapy depends on the trust established . . . , and sexual intimacy is a violation of that trust in the same way that incest is a violation of the trust in parenthood," she said. "The father or mother has the love and trust of the child, and even if a child is seductive or cute, it is up to the parents not to act out."

Bouhoutsos' report at the psychologists' annual convention in Anaheim, Calif., noted other findings about sex between therapists and patients that have come from her data and other studies not yet reported:

* By a 10-to-1 ratio, most of the patients involved are women. About half were not aware that it is unethical, and in many states illegal, for therapists to have sex with their patients.

* Only about 2 percent of the patients report sexual incidents to ethics committees and carry the reporting through all the necessary procedures. Of those who did report the incidents, a disproportionate number, about half, were male.

* Among therapists who had sex with their patients, it appears that 75 to 80 percent are "repeaters," having sex with more than one patient. The number of repeated offenses varies, and in one case Bouhoutsos said a therapist reported having sex with 100 patients.

The study described by Bouhoutsos began in 1978. To avoid having therapists to report on themselves or colleagues, Bouhoutsos sent questionnaires to all licensed therapists in California, asking them to report any incidents detailed by patients.

Of 4,300 questionnaires sent out, about 700 were returned, and 380 of those who responded described 560 incidents of sex between patient and therapist.

Though not all sexual incidents might be detected by that method, Bouhoutsos said she believes a large percentage were, because apparently 90 percent of such the victims seek help from a second therapist.

Other studies have shown that 6 to 8 percent of therapists and medical doctors have sex with their patients, according to Ivan N. Mensh, head of the division of medical psychology at the UCLA School of Medicine. Though rates up to 12 percent have been reported, that included what was called "non-erotic" intimacy as well, he said.

A 1977 study in which therapists anonymously reported their own sexual relations with patients found no difference in the sexual activities among different kinds of therapists--from humanists to Freudian analysts.

A study by Annette Brodsky, chief of psychology at the Harbor-UCLA Medical Center, and Jean Holroyd, a UCLA psychologist, also found that even among therapists who repeatedly had sex with patients, a majority believed it was bad for both therapist and patient, Holroyd said.

Because of a widely publicized case in California in which a college teacher advocated sex as a part of therapy, Mensh said, knowledge and interest in the subject has increased greatly in recent years.

Still, sex between therapist and patient is explicitly illegal in only 15 states, Bouhoutsos said, although therapists could be charged under other statutes in virtually all states.