A new term “chronic migraine” has been introduced, Code 1.5.1, and this refers to migraine headache occurring on 15 or more days per month for more than three months in the absence of medication overuse.^158,159  Another form of migraine is that which occurs as a consequence of substance withdrawal including triptans.  It is believed that at least 4 to 5 percent of the U.S. population currently has chronic headaches, many of which are so-called transformed migraine from the overuse of analgesics.  Medication-overuse headache (MOH) is coded as 8.2.  Previously, this was called rebound headache, drug-induced headache, medication-misuse headache.  It is by far the most common cause of migraine-like headache occurring greater than 15 days per month and of a mixed picture of migraine-like and tension-type-like headaches from the overuse of symptomatic migraine drugs and/or analgesics.  Roughly, if a patient is using medication 2 to 3 times per week, there is a tendency to develop medication-overuse headache (MOH).^160,161