Dissociatives are psychoactive substances that are said to reduce or even block signals to and from the conscious mind. While many drugs do this, dissociatives do this in a way that procures hallucinogenic reactions, often including dream-like states, trance, and mind-body dissociation.
Dissociatives are somewhat controversial in regards to the risks of their use. Physically, they are often not very dangerous, but mentally they may exhibit signs of bringing out mental trauma after a while, but these reports are neither common nor proven. The overall physical danger is probably between a 2 and 3 (with PCP, a 4 to 5 physical danger, being one of the only exceptions), while the mental danger could have as wide of a scale as a 1 to 4.