Anyone who takes painkillers for headache more than every second day, has medication overuse headache (MOH) by definition. This doesn’t mean painkillers are the only reason for headache, but there’s a good chance the headache will improve by taking less.
Kristofferson et al 2015 [1] taught GPs at 5 surgeries in Norway how to do a brief intervention, talking about medication overuse headaches for just nine minutes. 50% of the patients stopped having chronic headaches within two months compared to 8% in the control group.
The main risk factors for developing this type of headache is being a woman, between 30 and 50, with migraine. As the migraine gets worse, more painkillers are used, and together with headache come all the other symptoms of chronic pain: fatigue, low mood, concentration difficulties, hypersensitivity.
MRI has shown changes in the brainstem and prefrontal lobe, that go away when the headaches improve. Animal studies have shown changes in rat brains after daily painkiller use, but it’s not clear if that’s the same thing as medication overuse headache in humans.
All painkillers can cause it
Medication overuse headache was described in the 1930’s for patients using paracetamol, aspirin, barbiturates and ergotamine. It remained a problem over generations, as painkillers were replaced by codeine and NSAID and when triptans were added. We know that paracetamol, aspirin, and NSAID have lower risk and can be taken 3 days a week, but the others not more than 2 days a week on average. It’s been reported that the new gepant class of painkillers doesn’t cause MOH – but time will tell if this is correct.
Barbiturates and codeine are addictive, so it’s no surprise that withdrawal can cause headaches, but what about the other medications? What causes MOH?
Is it addiction?
Although this plays a role in overuse of codeine, most patients with MOH are not addicted in the physiological sense. That said, some of the same brain changes are seen, e.g. in the dopamine mesolimbic network. I’ve occasionally come across patients with drug seeking behaviour but that’s not the norm. [Galli]
Is it dose fluctuation?
It’s very rare for a person without underlying migraine or tension type headaches to develop MOH, and most patients with MOH started out with migraine. It seems that patients with migraine can develop MOH even if they start taking painkillers for another condition such as back pain. Given what we know about migraine hypersensitivity, MOH could be a consequence of fluctuations in drug levels, just like coffee, smoking or snacks can set off migraines. The weakness of this theory is that the medications used are not addictive, and doesn’t normally cause withdrawal like caffeine does.
Is it placebo?
Many studies on drug withdrawal in MOH are uncontrolled or unblinded, and most studies on migraine treatment show a large placebo effect, probably because just seeing a headache specialist frequently is good for headaches. While the Kristofferson study cited above and a few others show that this is not the only explanation, it’s likely that stopping medication works a lot better if you have supportive clinician who can advise on other ways of managing the headache.
Did the migraine just get worse for a while?
Another cause for placebo is if patients go to their doctor or join a study at a time when their migraine is particularly bad. Most will then revert to baseline over the next several months, and as the headache becomes better, they use less painkillers.
Again, the randomised studies show that withdrawal works, but it’s hard to rule out that MOH is caused in the first place by migraine getting worse for other reasons. It’s hard to test this, as it wouldn’t be ethical to give migraine patients daily painkillers.
Are drugs a distraction?
It’s also possible that taking painkillers for every headache, means never trying other ways of managing headaches. Stopping painkillers with the help of a clinician makes it necessary to find other ways, such as stress management, making changes at work or in relationships, sleep, exercise or other lifestyle factors. In this hypothesis, the painkillers harm by being a distraction.
Vulnerability / environment
In the end, like with almost every medical condition, it will come down to a combination of vulnerability related to genetics, co-morbidities and background, combined with too many pain killers and perhaps something other trigger. We’re unlikely to ever know for sure why, but stopping painkillers remains the most effective way known to reduce chronic headaches.
[1] Kristoffersen ES, Straand J, Vetvik KG, et al. J Neurol Neurosurg Psychiatry 2015;86:505–512.
[2] Galli F, Pozzi G, Frustaci A et al (2011) Differences in the personality profile of medication-overuse headache sufferers and drug addict patients: a comparative study using MMPI-2. Headache 51:1212–1227. https://doi.org/ 10.1111/j.1526-4610.2011.01978.x
[3] Chiang C-C, Schwedt TJ, Wang S-J, Dodick DW. Treatment of medication-overuse headache: A systematic review. Cephalalgia. 2016;36(4):371-386. doi:10.1177/0333102415593088
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