I didn't see this thread, but I came to the same conclusion last night.
Anandamide is also responsible for removing unnecessary short term memories.
I was analyzing my mental state after a hard day of work last night, and I realized that my memory functioned very similar to being high.
Also, the brain emits Dopamine as a pain killer which is also a big contributor to the runners high as well as the marijuana high, i'm pretty sure.