To equate reduced blood flow with Brain damage is insane, IMO! The fact that most folks who drink coffee daily are reducing their brain blood flow, as Charles S. points out ( https://www.ncbi.nlm.nih.gov/pubmed/19219847 ), means that most of the US population is Brain damaged from drinking coffee... NOT... so if they are drinking coffee and smoking pot daily... they should be brain dead for sure... NOT... Just stupid logic. Eastern meditating Yogis and other who have practiced the art of being able to down regulate their blood flow and other metabolic functions, can survive for extended time on very little oxygen, and no food or drink either. It is documented that some of these amazing meditative states are almost clinically dead, according to vital signs. None of them have ever been damaged mentally from such reduced blood flow, so reduced blood flow doesn't always equate to tissue damage! Don't read into, or assume negative conclusions based upon reduce blood flow to the brain... it probably happens every night and is essential to health and maintenance of the human body, and mind. That is true! End of story.