Stress activates a hormonal pathway in the body called the hypothalamic-pituitary-adrenal (HPA) axis (10). Activation of the HPA axis is associated with increased levels of cortisol and corticotropin-releasing hormone (CRH) (10). The HPA axis, cortisol, and CRH help control stress response in the body (10). CRH and cortisol release can suppress normal levels of reproductive hormones, potentially leading to abnormal ovulation, anovulation (i.e. no ovulation), or amenorrhea (i.e. absence of menstruation) (11-13). Furthermore, abnormal levels of CRH in reproductive tissue have been associated with negative pregnancy outcomes, such as preterm birth.
Dysmenorrhea (i.e. painful menstruation) has been linked to working in jobs that are low control, are unsecure and have low coworker support (24). Stress from the preceding month may also affect the frequency of dysmenorrhea (25), so someone might not experience painful menstruation as a result of stress until their period the following month. People with a history of dysmenorrhea may be more likely to experience this effect (25). Similarly, people experiencing stress earlier in their cycle were more likely to report severe symptoms during the time leading up to and during menstruation (26).
As mentioned, the different effects of stress may be, in part, due to timing. Higher reported stress during the follicular phase (i.e. from the first day of menstruation until ovulation) has been strongly associated with changes in normal reproductive function (25, 27). In one recent study, those reporting pre-ovulatory stress (during the follicular phase) were less likely to become pregnant as compared to those not reporting stress during the same time (27). This suggests that stress may cause the body to delay or entirely suppress ovulation. This idea is supported by research examining menstrual cycle variation.
The length of the luteal phase (i.e. post-ovulation until menstruation) tends to be consistent across and within women (29), whereas the length of the follicular phase has a stronger association with the variation in the total length of the entire menstrual cycle (29). This means that the follicular phase, as opposed to the luteal phase, is more likely to change in length. Therefore, the effects of stress on ovulation may be one of the biggest factors related to changes in cycle length due to stress.