First, many studies asked women to report their symptoms retrospectively, looking to the past and relying on memory, which is known to inflate reporting of PMS compared to what's called prospective reporting, which involves keeping a daily log of symptoms for at least two months in a row.
Primero, se pedía a las mujeres que en retrospectiva informaran de sus síntomas; que miraran al pasado confiando en la memoria. Se sabe que esto exagera las cifras del SPM con respecto al análisis prospectivo, que implica llevar un registro diario de los síntomas al menos durante dos meses seguidos.