These are voluntary reports from health care providers and consumers linking DMAA use to seizures, arrhythmias, heart attacks, strokes, panic attacks, and deaths, along with exacerbation of psychiatric conditions.

FORBES: Is DMAA Dangerous To Your Health?

He enriched the oxygen or the carbon dioxide in the air breathed by experimental subjects and found not a hint of suppression or exacerbation of yawning compared with control subjects breathing normal air.

WSJ: Matt Ridley on Why You Just Yawned | Mind & Matter