Although phencyclidine abuse is not associated with the development of physical dependence, it does give rise to a marked psychological dependence. A single dose, usually smoked with tobacco or other materials, can provoke a serious toxic psychosis, schizophrenic in character and accompanied by delusions, mental confusion and violent aggressive or self-destructive behaviour. Total personality changes are not uncommon, and flashback episodes occur frequently. Even total catatonic reactions are common. The unpredictability of its effects and its frequent adulteration with other hallucinogens add to the already considerable risk that is taken by anyone who tries the drug.