It was too little for Janis to feel but enough, the theory goes, to stimulate the brain's natural painkillers.
And some of these strategies may even trigger the body's natural painkillers, having the added benefit of making you feel good.
Realistic optimism fuels the body's immune system and triggers natural painkillers.
In humans it's thought to stimulate the body's own natural painkillers.
His final entry describes love as "the most natural painkiller what there is."
For example, there is some evidence that a static magnetic field can cause the release into the blood of beta-endorphins, the body's natural painkillers.
I asked Silberstein if this meant that the brain's natural painkillers were better than ones bought over the counter.
Exercise improves blood flow and produces endorphins, the body's natural painkillers.
Another theory is that stimulating the nerves may help the body produce natural painkillers called endorphins.