Most of us think of melatonin as a supplement for insomnia. It’s the hormone that the pineal gland in the brain produces with onset of darkness, and it’s suppressed by the light of daytime (or also artificial lights, particularly artificial blue light—which is one good reason to turn all unnecessary lights off a good half hour before bedtime, and avoid screens during that time too. If you can’t do this, at least red-shift your screens about a half hour before your bedtime.)
But it turns out, melatonin does a lot more than just initiate sleep. It’s also a powerful antioxidant, and as such, it’s gotten some attention recently for its role in decreasing oxidative stress in the lungs due to viral infection.
It also modulates pain, via a number of different mechanisms.
Sleep and Pain
Also, normalization of the circadian rhythm is itself associated with improvement in chronic pain.
Melatonin Interrupts Pain Signaling
Melatonin also interferes with pain signaling in various ways.
It decreases levels of second messengers called cAMP and cGMP, which without interference go on to carry chronic pain signals.
It inhibits arachidonic acid, whose downstream products (inflammatory prostaglandins) are the target for NSAID pain medications.
It increases the release of endorphins from the pituitary, which bind to opiate receptors.
Possibly related to this, since calcium channels are usually stimulated by excitatory glutamate and inhibited by calming GABA, melatonin also binds to GABA receptors, and increases GABA concentration by 50%. In addition to its anti-anxiety and sleep modulating effects, the calming neurotransmitter GABA is also analgesic in its own right.
Melatonin and Headaches
Melatonin has been studied for migraines, cluster headaches, and tension headaches.
This study showed that 3 mg of melatonin at bedtime has a prophylactic effect upon migraines, decreasing their severity, frequency, and duration. (Of course this is just symptom management—you always want to treat the cause—but symptom management can be nice in the meantime!)
This study shows that those who suffer from cluster headaches also have lower levels of melatonin. Circadian disruption may in fact be part of the root cause for cluster headaches. For this reason, melatonin is often recommended as a preventative measure for cluster headaches.
A trial of three months of 3 mg melatonin was also shown to decrease tension headaches by 50% or more. (Since tension headaches are also often associated with stress, I suspect some of that might have had to do with improved adrenal function resulting from deeper sleep).
Melatonin and the Gut
The gut also produces melatonin in the gut, via the same cells that produce its immediate precursor, serotonin (enterochromaffin cells). Its job there is to decrease inflammation and stimulate gut motility.
Because of this, melatonin is also studied for abdominal pains in IBS, and has been shown to be effective. While true treatment of IBS requires finding and treating the cause, melatonin may be a helpful adjunctive treatment in the meantime.
For many types of pain and through many different mechanisms, melatonin may be a helpful adjunctive therapy, without some of the significant side effects as other long-term pain medications. Of course, treating the root cause should also be a priority.
Those who do have side effects sometimes report vivid dreams, a “hung over” feeling in the morning (which diminishes with the dose), or rarely it can actually cause sleeplessness.