induce psychotic symptoms include amphetamine , caffeine (which can worsen psychotic symptoms in schizophrenia and produce olfactory hallucinations at very high doses in normal volunteers), cannabis , cocaine , desoxypipradrol , dimethyltryptamine , alcohol (ethanol), inhalants , gammahydroxybutyric acid (and its precursors gammabutyrolactone and 1,4-butanediol ), ketamine , LSD , mephedrone