Premenstrual syndrome: an exploratory trial suggests a benefit from kamishoyosan

A trial focused on self-reported symptoms

The researchers assessed the efficacy and safety of kamishoyosan, taken orally for three menstrual cycles. The study was randomized and open-label: the treatment received was not concealed. The abstract does not specify the treatment or follow-up offered to the comparator group.

The primary outcome was the change in the total premenstrual score on the Menstrual Distress Questionnaire, or MDQ. Secondary outcomes included a daily symptom questionnaire, the impact on activities and work, as well as sleep and heart rate.

Reported improvement, but no quantified magnitude

The abstract reports a statistically significant improvement in the premenstrual MDQ score after treatment. Some questionnaire domains also improved, including pain, concentration, behavioral changes and negative emotions.

The daily questionnaire also suggests reductions in irritability, anxiety, emotional instability and several physical symptoms. The activity limitation score was lower in the kamishoyosan group.

These findings are a favorable signal, not a clear measure of the expected benefit. The abstract provides neither numerical differences between groups nor uncertainty intervals. It is therefore impossible to determine whether the improvement would be large enough to make a meaningful difference to patients’ daily lives.

The lack of blinding limits interpretation

When participants know which treatment they are receiving, their expectations can influence their reported symptoms. This limitation is particularly important here, since the primary outcome relies on a questionnaire. Randomization does not eliminate this bias.

Only one adverse event was considered related to kamishoyosan: a headache. With 50 participants and follow-up limited to three cycles, this finding is not enough to establish long-term safety or rule out rare effects.

What we can take away

This trial warrants further evaluation of kamishoyosan, but is not enough to make it a recommended treatment for premenstrual syndrome.