a wide range of drugs whilst not causing a true physical dependence can still cause withdrawal symptoms or rebound effects during dosage reduction or especially abrupt or rapid withdrawal. these can include caffeine, stimulants, steroidal drugs and antiparkinsonian drugs. it is debated whether the entire antipsychotic drug class causes true physical dependency, a subset, or if none do. but, if discontinued too rapidly, it could cause an acute withdrawal syndrome. when talking about illicit drugs rebound withdrawal, especially with stimulants, it is sometimes referred to as "coming down" or "crashing".