The dried leaves and flowering tops of the Cannabis sativa or Cannabis indica plant. Cannabis contains active chemicals called cannabinoids that cause drug-like effects all through the body, including the central nervous system and the immune system. Cannabis is commonly used as a recreational drug. People also commonly use cannabis for multiple sclerosis (MS) and nerve pain. It is also used for nausea, vomiting, migraine, and many other conditions, but there is no good scientific evidence to support these uses.