Stress and extreme weight fluctuations may cause the menstrual period to arrive a week early, according to CNN. For some women, antidepressants, thyroid disease or polycystic ovary disease is the culprit.
Age also plays a role in early periods, according Everyday Health. It may take several years for teens to develop consistent menstrual cycles. On the other end of the spectrum, women near menopause may also experience irregular cycles.
If a woman experiences severe pain, heavy bleeding, mid-cycle bleeding or if the irregular menstrual cycles continue, she should see a healthcare provider as soon as possible, according to the Mayo Clinic. In some cases, physicians prescribe birth control pills to regulate the cycle.