The fact that a study and an editorial on premenstrual syndrome appeared in the New England Journal of Medicine last month is at least as important as what the study said.

Premenstrual syndrome, one might say, has arrived.

Of course, the millions of women who suffer from it -- and who have suffered from it down through the ages -- could have told the journal a few things a long time ago.

But since PMS has become a major topic of discussion, one of the problems has been to separate anecdote from scientifically accepted fact. For the past several years physicians and researchers, under increasing pressure from increasing numbers of women, have subjected it to intense scientific scrutiny. Result? At least as much controversy and confusion as ever. The most popular treatments -- including progesterone hormone therapy, vitamin B6 (shown to cause nerve damage in high doses) and anti-anxiety drugs -- have not been proved effective.

Even the New England Journal study -- in which a group of women with "unequivocal" PMS appeared to improve when hormonal manipulation supressed ovarian activity -- is regarded as important mainly in terms of research, rather than treatment. Hormonal manipulation is a radical and potentially dangerous procedure.

But one thing seems to have been established: Up to 40 percent of women suffer from distinct physiological and behavior symptoms in the few days before the onset of menstrual periods. The symptoms and their severity vary widely, but they are real. PMS lives.

Common physical symptoms include headaches (especially migraines), bloating, breast tenderness, fatigue, acne and constipation. Behavioral symptoms: food cravings (usually for sweets), crying jags, irritability, panic attacks, depression, mania, uncontrollable rages and, some say, uncontrollable acts during those rages.

In the old days, these symptoms were usually dismissed as "all in your head, my dear," suggesting, of course, that they were imaginary.

Curiously, research from the leading edge of science now suggests that PMS may indeed be "all in your head." But that no longer translates into "imaginary." Instead, it has to do with the discoveries about the effects of environment, or even perceptions, on brain chemicals (neurotransmitters) that carry messages between neurons and, in that way, regulate mood and behavior.

The hormones that regulate reproductive cycles in both men and women have their impact on the brain and dictate not only courting behaviors, say scientists, but a wide variety of moods as well.

PMS studies demonstrate a particularly large placebo effect, up to 80 percent in some cases, notes Dr. David R. Rubinow, a psychiatrist heading a program on premenstrual syndrome at the National Institute of Mental Health. This means that test subjects taking an inactive substance, although not knowing what they are really taking, tend to respond as well as those on the substances being tested.

This suggests nothing untoward about the mental health or stability of the subjects, nor does it denigrate the seriousness of the symptoms. "It simply demonstrates that this is an integrated disorder that includes perceptions and biologic dysfunctions," Rubinow says. "An effective study has to include both biology and perceptual and psychological variables . . . that can determine the expression of symptoms and may very well play a role in whether symptoms appear."

Rubinow recently participated in an intensive international five-day "think-tank" on premenstrual syndrome held in Philadelphia. It was sponsored by the National Science Foundation.

Proponents of some of the most widely touted treatments were either present or had papers presented at the meeting, the latter including Dr. Katharina Dalton, the London physician whose testimony in several highly publicized British trials raised the possibility of PMS as a legal defense.Preliminary results from the conference emphasized the lack of any single successful treatment for PMS, the still unknown nature of its cause, the continuing concerns about its role in the law and its effect on the women's movement.

There is also concern that, until ongoing scientific studies are concluded, women be wary of popularized therapies. As Dr. Judith L. Vaitukaitis of the Boston University School of Medicine wrote in the recent journal editorial, ". . . many women are so desperate that they will seek out any form of therapy. Unfortunately, that has resulted in the development of clinics specializing in PMS which are being merchandised like many of the fast-food chains . . ." Getting Help

For diagnosis and treatment of premenstrual syndrome:

* Dr. David R. Rubinow, National Institute of Mental Health, treats PMS with several substances, including vitamin B6, hormone therapy and anti-depressant drugs. 496-9675.

* Dr. Elisabeth Herz, George Washington University Medical Center, offers mostly non-drug treatments. 676-8487. PMS Treatment Center, 507 N. Frederick Ave., Gaithersburg. (301) 330-2666.

Some books:

* "PMS: Premenstrual Syndrome and You," by Niels H. Lauersen M.D. and Eileen Stukane. (Pinnacle, 224 pp., $3.95).

* "PMS: Premenstrual Syndrome," by Ronald V. Norris M.D., with Colleen Sullivan (Berkeley, 338 pp., $3.95).