Cannabis is one of the important food and textile resources that has been used since 4000 BC. The fact that it was used as a medicine by the Chinese caused it to be included in the oldest pharmacopoeia in the world. However, in the 20th century, marijuana production from cannabis was a turning point in cannabis history, and then led to the limitation of cultivation areas and use. Today, cannabis is the most popular illicit drug worldwide. Regular use of cannabis is associated with impaired functioning, decreased academic performance, a motivation, addiction and, psychiatric disorders like psychosis, schizophrenia and mood disorders. On the other hand, recent research proposed promising therapeutic potential of cannabis-based drugs for a wide range of medical conditions including neurological and psychiatric disorders. These findings have led to the legalization of medical use of cannabis in certain states of the United States and in certain European countries. In this review, cannabis use, the historical process of cannabis use, medical use of cannabis, possible consequences of medical use of cannabis and the reflections of cannabis-related policy changes on society will be discussed.