9. 4-MTA
Addiction rate: 1.3
Since it contains a high level of serotonin, this drug, among he other least addictive drugs on our list, causes euphoria and happiness a short time after it is used. However, it can also cause hypothermia and organ failure, so it is stated as the cause of many deaths–although it has never been tested on humans in the laboratory.
David Smart/Shutterstock.com
