They help control pain and emotions.
> These areas have a rich supply of a chemical called dopamine.
>
> Doctor Rosen said the reduced blood flow may lead to changes in
> dopamine. This, in turn, leads to a reaction that releases
> endorphins. These brain chemicals reduce pain and help fight
> feelings of sadness.

Yeah but... these chemicals are only temprorarily released, and
acupuncture patients claim permanent healing. This still doesn't
explain it.