Vivid auditory hallucinations and paranoid delusions are the real frighteners and, unlike hallucinogens, the "trip" cannot be turned around. This is a very real mental state caused by over-excitement of the brain's fright centers.
Its effects often start with curiosity, deep thought, and paranoia. Its slow buildup makes it all the more dangerous, as it is harder to recognize the symptoms.
Some users become obsessed and get into activities like, ironing or scrubbing floors through the night, or dismantling and reassembling electrical equipment.
While amphetamine psychosis is much more common among heavy regular users, there are real dangers that any small amount of speed used by a person with schizophrenic tendencies could push them over the edge.