When medicine makes headaches worse

For many of us, it's a natural response: you have a headache, so you take some painkillers. If the pain comes back, you repeat as necessary.

Though that may be fine for a day or two, taking headache tablets any more than that can have unexpected and serious consequences. In fact, overusing painkillers can perpetuate headaches, making them return as soon as the medication wears off. And when that pain comes back, the natural response is to take more painkillers -- maybe the worst thing you could do.

To break the cycle, you must stop taking the medication. However, that can cause days, weeks, or even months of agonising symptoms, including headaches and fatigue. It often requires other medications, and sometimes admission to hospital, to help you get through it.

Who knew that that innocent-looking little pack in your medicine cabinet could cause all that?

Difficult diagnosis

The organisation Headache UK says 10 million of us suffer regularly from migraine and other headaches.

Many people will have rebound headaches, also called medication overuse headaches. Though they may be less frequent than migraines -- which affect about one in four women and one in 12 men -- rebound headaches cause a great deal of preventable suffering.

Although experts still don't know exactly what causes rebound headaches, the regular overuse of pain medication can cause physiological changes. Using too much of a painkiller seems to lower a person's pain threshold so that they begin to require painkillers to feel "normal".

"I believe that overusing painkillers actually lowers the level of serotonin, a chemical in the brain", says headache expert Dr Seymour Diamond. A decreased level of serotonin can change how a person experiences pain.

Part of the problem with rebound headaches is that they are sometimes difficult to identify, especially since people with rebound headaches usually had chronic headaches to begin with (which is precisely why they started to take medication). Noticing the shift from a migraine headache to a rebound headache may be difficult for patient and doctor alike.

However, the symptoms can be somewhat different. The nausea and sensitivity to light that are typical with migraine headaches are usually absent in rebound headaches, and the pain can be anywhere on the head.

"The typical patient with rebound headaches will come in and complain that he has headaches every day", says Professor Michael Gallagher, head of a leading headache centre. "The pain will escalate to a point where it's interfering with his life and he's suffering from depression and anxiety, and simply not feeling like himself anymore."