Some of the causes of early periods include hormone imbalances, stress and diet. Birth control can also cause early or irregular periods.
The female body produces estrogen and progesterone, which are responsible for ovulation and menstruation. When the body produces weaker or stronger than normal hormones, periods can become more frequent, heavier than usual or spaced apart more than 28 to 30 days, according to Epigee Women's Health. Since birth control contains these hormones, it can cause frequent or irregular periods. A poor diet can also affect the amount of the hormones that are produced. Women should talk to their doctor if the menstrual cycle changes or is causing discomfort.