We examined data from a community sample and a clinical cohort to generate empirical evidence that would inform the DSM-5
sub–Work Group regarding criteria for PMDD. Hypothesis 1 was supported by both samples in that the peak of symptoms included premenstrual and menstrual days, although the frame differed by 1 day in the respective cohorts. These findings held for physical symptoms, affective symptoms, and functional impairment. Our results are in accord with findings from a large health maintenance organization population,9
where women showed a peak of symptom severity either the day before or the first day of menses. Interestingly, women with the most severe symptoms were most likely to reach a zenith the day before menses, while women with less severe symptoms had the worst symptoms on the first day of menses. If women in our clinical cohort have more severe symptoms than those in the community, which is a reasonable assumption, our results would have great consistency with this prior study. Notably, the criteria for PMDD outlined in DSM-IV
accommodate this interval because DSM-IV
stipulates that symptoms occur in the “last week of the luteal phase and remit within a few days of the onset of the follicular phase.”7
The implication of this analysis is that clinicians and researchers may consider the measurement of symptoms from 4 days before through the first 3 days of menses rather than the traditional method of measuring symptoms of PMDD during the premenstrual week only.
We also found that our second hypothesis, that DSM-IV includes symptoms highly associated with a premenstrual disorder, was supported. Regardless of the data set and perimenstrual interval selected, the symptom of mood swings was among the most severe of the 4 affective symptoms listed in DSM-IV, 1 of which is required for a diagnosis of PMDD. Depressed mood was the least severe in this group. This introduces the possibility of listing mood swings first among the symptom criteria rather than depressed mood, because the latter implies that depressed mood is the most common symptom of the disorder. However, our study did not determine whether mood swings are a symptom specifically associated with PMDD or a symptom more commonly experienced by women in general when they are premenstrual. If future analyses are able to confirm that this symptom is highly associated with PMDD, it may warrant higher listing among the possible symptoms. It should be noted, however, that breast tenderness and bloating were highly related to the menstrual cycle in both cohorts. Given that the DSM focus is on emotional conditions, the Work Group may prefer to not indicate this as the first symptom in the criteria list.
In our exploration of the optimal number of symptoms that reflect functional impairment, results differed greatly according to the cohort. An optimal cutoff of 2 was found for the community cohort, while a cutoff of 7 was suggested for the clinical cohort. Differences in the characteristics of subjects likely contributed to this in that the women in the clinical cohort were treatment seeking and were more likely to have had severe symptoms. Our method of choosing an optimal cutoff point for the number of symptoms places equal consideration on sensitivity and specificity. Sensitivity, the probability of symptoms above the cutoff given impairment, is very low at higher scores in the community sample because there are few women in this sample with many symptoms. In the clinical sample, however, there are more symptoms generally and more symptoms in the impaired group, so sensitivity remains strong at higher cutoff points. Specificity, the probability of staying below the cutoff in patients without impairment, is sufficiently high for low cutoff points in the epidemiologic sample because of low numbers of symptoms in the group without impairment. The clinical sample has more symptoms in the group without impairment, and a higher cutoff is required to achieve high specificity. We think that weighing these 2 estimates equally is a compromise suitable for future use with a wider group of patients who may be less symptomatic than our clinical sample but more symptomatic than the overall population.
Our best estimate after combining the 2 cohorts was an optimal cutoff of 4 symptoms.
The American College of Obstetricians and Gynecologists definition of premenstrual syndrome requires only 1 symptom that is present within 5 days of the onset of menses and ends within 4 days of the menstrual flow, causes functional impairment, and is documented in 3 menstrual cycles. This definition may be more in line with what we found in our community sample. This issue requires greater exploration because if the DSM-IV requirement for 5 symptoms is retained, many women may not be diagnosed as having PMDD if they have 3 or 4 symptoms perimenstrually, even if they have impairment.
Our analyses have several limitations that should be considered. The most obvious is that the 2 cohorts used in this secondary analysis are different in a variety of ways. While we did not combine them when we tested hypotheses 1 and 2, we did for our exploratory analysis. A second consideration is that we used a statistical parameter, the effect size, to derive what we would consider a meaningful symptom. However, symptoms are subjective and this parameter, in particular the cutoff of 1, may not reflect a clinically significant difference. On the other hand, the fact that the application of an effect size of 1.0 for symptoms correlated with an effect size of 1.0 for functional impairment suggests that this cutoff is reasonable. Finally, our exploration of perimenstrual dates meant that we needed data from the first few days of a third menstrual cycle for subjects and we only had 1 or 2 cycles that included the first few days of menses for some subjects. Thus, we did not require that changes be shown across several menstrual cycles, which would have been a very rigorous test of PMDD criteria and is stipulated by DSM-IV. The need for 2 or more menstrual cycles to further validate the criteria for PMDD should be assessed in future work.