- Often represents transformation of a primary headache syndrome→ typically migraine or tension type
- Also associated w/overuse of medications (e.g. NSAIDs, barbiturates, narcotics, other) for treatment of acute headache
- Can also be a primary chronic HA disorder (i.e. not transformed or related to medication overuse)
- Overuse of headache medications
- Headache 15d/m for 3m
- If related to transformation of primary HA, maintains some of characteristics of original HA (e.g. migraine), though not as severe
- Can also have "mixed" features (e.g. sx of both tension and migraine)
- Chronic daily HA are characterized as short (< 4h) or long (>4h) duration