People who take narcotic painkillers such as oxycodone and codeine too often to treat their migraines may be doubling their chances of having chronic headaches a year later, a new study has found. But researchers say that people who use other types of pain meds--including triptans or nonsteroidal anti-inflammatory drugs (NSAIDs)--don't appear to increase their chronic-headache risk. Experts say these findings suggest that strict limits for these types of drugs should be enforced among migraine...