If you have frequent migraine headaches, you may suffer from chronic migraines. According to the International Headache Society (IHS), a person who suffers from chronic migraines has at least 15 headaches per month over three months, of which at least eight are migraines. While research is still somewhat inconclusive, doctors have found that chronic migraines are related to genetics, gender, and changes in brain chemicals and abnormal brain activity. Research has also shown that women are more likely to suffer from chronic migraines. Specific causes of migraine headaches include lack of sleep, excessive caffeine consumption, stress, and hormonal changes during pregnancy and menopause.