In this longitudinal study, women with high stress in the previous month were significantly more likely to report an increased number and severity of perimenstrual symptoms in the subsequent cycle. Changing stress levels across the two cycles were associated with a changing pattern of symptom severity. Among those whose stress levels changed from one cycle to the next, more moderate/severe symptoms were reported during the cycle that was preceded by higher stress levels. Although the sample size of the subgroups in this analysis was small, this certainly suggests that stress patterns may be associated with differing perimenstrual symptom patterns. For those who experienced high stress levels preceding both cycles, it is possible there is a cumulative effect of chronic stress on symptom severity, as 50% of these women reported ≥8 moderate/severe symptoms in the second cycle, up from 27% in the first cycle, although a longer longitudinal study would be necessary to fully explore this relationship. Furthermore, we are unable to differentiate the stress measured in this study as either chronic or acute, and these types of stressors may exert different effects on the menstrual cycle.
Our study is subject to several limitations. First, our assessment of perimenstrual symptoms was based on a weekly collection of symptoms rated for severity. We expect that recall of symptoms from the prior week is not subject to substantial recall error because of this limited time period. Although gold standard diagnosis generally requires prospective collection of daily symptoms for two cycles,40
most previous studies of this association used monthly or yearly recall of symptoms.4,41–47
Weekly symptom collection is an alternative to daily collection that is thought to reduce participant burden and increase compliance without involving long-term retrospective recall.11
Furthermore, whereas retrospective assessments of PMS have been criticized for the potential for participants to inflate the severity of symptoms, these criticisms apply mainly to retrospective assessments that reflect an entire menstrual cycle or several cycles and rely solely on memory to differentiate between phases of the cycle.48
The current study required women to recall symptoms over the past week and did not require women to recall over multiple phases of the cycle. However, we acknowledge the limitations associated with weekly reporting of perceived symptom severity. To this end, it was not our intent to diagnose participants with overt PMS but to analyze and describe the longitudinal association between stress and perimenstrual symptom patterns.
In addition, it is possible there is a circularity to the association between high stress and high symptom severity, in that stress may contribute to increased PMS symptom severity, which may in turn cause higher stress levels during the premenstrual period. We attempted to minimize this potential bias, however, by using the stress measure from the symptom-free interval (i.e., late follicular phase/early luteal phase) that preceded the premenstrual time period as the exposure. It is less likely that stress experienced during the symptom-free interval could be fully attributed to PMS symptoms. Finally, although our analysis is longitudinal by design and the stress assessments preceded that of the perimenstrual symptoms, we cannot delineate causality nor fully rule out reverse causality.
This study also has many strengths. Longitudinal analysis allows for the determination of a temporal association between perceived stress and perimenstrual symptoms in the next cycle, which previous cross-sectional studies were not equipped to analyze. We were also able to examine the effects of changing stress levels on premenstrual symptom severity. Our study was conducted exclusively among healthy, reproductive-aged women with no psychological or other chronic diseases, many of which conditions served as confounders in previous studies, as they mimic PMS symptoms.11
Other studies included women on oral contraceptives or antidepressant medications, often prescribed as a treatment for PMS/PMDD and associated with decreased severity of symptoms.49–51
Finally, our study was able to time clinic visits to specific phases of the cycle with the aid of fertility monitors tracking hormone levels across the cycles.
Results from this longitudinal study add to results of a small number of cross-sectional studies that have reported a positive association between psychosocial stress and premenstrual symptoms.4,41–47,52,53
There has been only one similar longitudinal study, and that study found that women with high stress levels during the previous month, particularly during the follicular phase, had increased risk of dysmenorrhea (painful menstruation).54
In contrast, no predictive value of daily stress was found in a small cohort of 25 women with severe PMS, although the full range of severity was not considered; there was no comparison group of women without PMS; and estimates were not adjusted for confounders.55
Other studies have found that past traumatic experiences were associated with greater severity of PMS symptoms.56
Moreover, the percentage of cycles where at least one moderate symptom was reported and the percentage classified as moderate/severe PMS in our study were similar to those reported in other studies.5,46,57
It is not clear how stress may contribute to increased perimenstrual symptom severity, although stress-induced changes in ovarian hormone levels and neurotransmitters may be involved. Stress has been shown to cause hormonal changes through the HPO axis, causing alterations in ovarian hormones that may render a woman more susceptible to menstrual disorders.58
Alternatively, Rabin et al.59
have suggested that PMS was related to an activation of the hypothalamic-pituitary-adrenal (HPA) axis or a heightened sensitivity to its function, in that those who are more sensitive to increased cortisol are those who develop PMS.59
A third potential mechanism relates to the impact of stress levels on the neurotransmitters epinephrine, norepinephrine, and serotonin, which have also been shown to be altered in women with PMS.16,19,62,63
Woods et al.53
found that increased cortisol levels were associated with increased fluid retention and related symptoms (i.e., body aches, bloating, swelling, breast tenderness) and that altered levels of norepinephrine and epinephrine were associated with anxiety and mood-related symptoms. Finally, it has also been suggested that the stressed physiological state leads to a heightened sensitivity to an increased severity of menstrual symptoms.64
Overall, these results extend those of previous cross-sectional studies suggesting that the severity of perimenstrual symptoms may be stress-related. Results are likely generalizable to populations similar to our healthy, reproductive-aged women without diagnosed PMDD. Given the increased direct and indirect healthcare and occupational costs associated with PMS,1,2
we agree with Wang et al.54
that stress reduction programs for reducing psychosocial stress may be a potentially noninvasive and cost-effective method for PMS relief compared with pharmaceutical treatments.