Amphetamine psychosis is the result of binging on amphetamine (usually methamphetamine) for several days straight. Clinically, it is similar to paranoid schizophrenia.
Amphetamine psychosis causes delusions and paranoia. Some common delusions are: bugs crawling on your skin, police hiding in the bushes, strangers following you around, people spying on you, etc. The delusions are ongoing and cannot be corrected by reasoning.