J Manipulative Physiol Ther 1999 (Nov); 22 (9): 582–585 ~ FULL TEXT
Maxwell J. Walsh, BAppSc, Barbara I. Polus, PhD, BAppSc
Department of Chiropractic,
Osteopathy and Complementary Medicine, RMIT,
OBJECTIVE: To evaluate the efficacy of chiropractic therapy on the treatment of symptoms associated with premenstrual syndrome.
DESIGN: A prospective, randomized, placebo-controlled, crossover clinical trial.
SETTING: Multicenter private clinics.
SUBJECTS: Twenty-five subjects with diagnosed premenstrual syndrome (with a Moos premenstrual syndrome questionnaire plus daily symptom monitoring).
INTERVENTION: After randomization, 16 of the subjects received high-velocity, low-amplitude spinal manipulation plus soft tissue therapy 2 to 3 times in the week before menses for at least 3 cycles. The remaining 9 subjects received a placebo treatment with a spring-loaded adjusting instrument wound down for minimum force. After a 1-cycle washout, the 2 groups changed over.
OUTCOME MEASURE: Daily rating of symptom level, comparing total scores for premenstrual week with baseline for treatment and placebo phases. DATA ANALYSIS: The data were analyzed with paired Student t tests and Wilcoxon signed rank tests, with the statistical significance set at P < .05.
RESULTS: There was a significant decrease in scores after treatment compared with baseline scores (P = .00001) and a statistically significant decrease in scores for the treatment phase compared with the placebo (P = .006). For group 1 (n = 16), there was a significant decrease in scores after treatment compared with baseline scores (P = .0001) and a statistically significant decrease in scores for the treatment phase compared with the placebo (P = .041). For group 2 (n = 9), there was a significant decrease in scores during treatment compared with the baseline (P = .01); however, there was no difference at the P = .05 level between treatment and placebo scores.
CONCLUSION: Within the limitations of the study, the results support the hypothesis that the symptoms associated with PMS can generally be reduced by chiropractic treatment consisting of adjustments and soft-tissue therapy. However, the role of a placebo effect needs further elucidation, given that the group receiving the placebo first, although improving over the baseline, showed no further improvement when they had actual treatment.
From the FULL TEXT Article
The results of the study support anecdotal and case study evidence that chiropractic therapy consisting of spinal manipulation and soft-tissue therapy can reduce symptom levels in some women with PMS. Just over half of the subjects who completed the trial showed a significant improvement in symptom levels after treatment.
There are a number of limitations to the study that need to be taken into account in applying the trial results to the general population of women with PMS. The relatively small sample size, although large enough for statistical purposes, makes it difficult to apply the results to the general population, despite the appearance that the study sample was a representative sample. As a result of the long trial period (each subject was required to be in the study for a minimum of 9 months), compliance was difficult; a large number of participants dropped out, with the effect on the results not known. Follow-up effects were not obtained so that the longer-term effects of the treatment are not known. Informal indications from subjects were that the effects were short-lived, with regular treatment needed on a monthly or bimonthly basis. This aspect requires further investigation. The inability to blind the treating practitioners to the type of intervention delivered is a problem associated with all manual therapy trials. Similarly, the development of an appropriate placebo has been a major problem. The placebo in this trial involved the use of a spring-loaded, adjusting instrument that was turned down maximally to minimize the impulse delivered away from the normal point of contact. Haas et al  found that this procedure was satisfactory. However, it can be argued that it is impossible to remove all effects of a placebo used in manual therapy trials; this would account for a part of the apparent placebo effect with group 2. In general, the presence of the Hawthorne effect, in which the construct validity of a study is compromised by the introduction of subjects' and practitioners' expectation bias, would con-tribute to a possible placebo effect.
There are several theoretical models that could provide a basis for the role of chiropractic treatment in PMS management. Normalizing neurologic activity is a fundamental premise of chiropractic treatment. [19, 20] In particular, the somatovisceral reflex hypothesis states that somatic sensory input arising from the richly innervated soft-tissue structures of the vertebral motion segments may initiate or modify a visceral activity such as abdominal cramping and vascular headaches. [21, 22]
A more recent hypothesis involves the role of endogenous opiate peptides. There is evidence that aberrant cyclic changes in circulating endogenous opiate peptide levels may play a role in the pathophysiology of PMS. In particular, an excessive drop of endogenous opiate peptides during the premenstrual weeks in women with PMS has been found, which may account for a number of PMS symptoms.  Chiropractic manipulative therapy may cause a change in ß-endorphin (an endogenous opiate peptide) levels. This has been used to explain the pain relief obtained from chiropractic manipulative therapy. [24, 25]
A further theory implicates prostaglandins in PMS. Abnormal production of prostaglandins has been found in women with PMS. Abnormal prostaglandin levels can give rise to symptoms similar to those found in PMS.  There is some evidence that spinal manipulation may be associated with a reduction in plasma levels of prostaglandins. 
Within the limitations of the study, the results support the hypothesis that the symptoms associated with PMS can generally be reduced by chiropractic treatment consisting of adjustments and soft-tissue therapy. However, the role of a placebo effect needs further elucidation, given that the group receiving the placebo first, although improving over the baseline, showed no further improvement when they had actual treatment.