I found out recently what killed a promising student in my program this past year. His heart was stopped by synthetic marijuana. I have no idea why he was using it, I only know that it killed him. He was a promising young man with significant ability that is now lost. He left behind a son that he cared deeply for. One of his motivations for learning a trade was to improve life for his family. I admittedly know very little about this stuff, so I am providing some links to articles about it. Wikipedia Article National Institute of Health
What I do know is that it makes no sense to inhale any kind of drug laced smoke into your body. Before FDA approved drugs are even tested in limited quantities on people, they are extensively tested in animals for safety. With these designer drugs, the customers are the lab rats. My message is simple: if you use this stuff - stop. If you know someone else who uses it - stop them. It is literally a matter of life and death.