A new study suggests that a woman's monthly menstrual cycle could prove helpful in understanding common mental health problems that develop in women.

Researchers from the University College London state that during a woman's monthly menstrual cycle, she becomes more vulnerable to some of the psychological side-effects associated with stressful experiences. This is partly because there is a change in hormone levels in the body during this period. Hence, authors of the new study suggest that this period could be used by them to better understand common mental health problems that develop in women.

Researchers of this study also found a potential link between psychological vulnerability and the timing of a biological cycle, in this case ovulation. They also discovered a series of "intrusive thoughts" as symptoms of mood and anxiety problems, which usually occur when someone goes through a stressful experience.

For the study, researchers called on 41 women aged between 18 and 35. All participants had regular menstruation and were not using pills as contraceptives. In the course of the study, all these participants were made to watch stressful movies about murder or death. Immediately after watching the movie, they were asked for a salvia sample to determine their hormone levels. They were also asked to record any "intrusive thoughts" about the movie that came to them in the following days.

"We found that women in the 'early luteal' phase, which falls roughly 16 to 20 days after the start of their period, had more than three times as many intrusive thoughts as those who watched the video in other phases of their menstrual cycle," explains author Dr Sunjeev Kamboj, Lecturer in UCL's Department of Clinical, Educational and Health Psychology. "This indicates that there is actually a fairly narrow window within the menstrual cycle when women may be particularly vulnerable to experiencing distressing symptoms after a stressful event."

Authors of the study state that these findings could give them a better understanding of mental health problems and their treatment in women who have suffered trauma.

"Asking women who have experienced a traumatic event about the time since their last period might help identify those at greatest risk of developing recurring symptoms similar to those seen in psychological disorders such as depression and post-traumatic stress disorder (PTSD)," said Dr Kamboj. "This work might have identified a useful line of enquiry for doctors, helping them to identify potentially vulnerable women who could be offered preventative therapies. However, this is only a first step. Although we found large effects in healthy women after they experienced a relatively mild stressful event, we now need to see if the same pattern is found in women who have experienced a real traumatic event. We also need further research to investigate how using the contraceptive pill affects this whole process."