Overview Delusions false beliefs firmly maintained in spite of indisputable and obvious proof to the contrary not shared with other members of patient's culture/subculture e.g. thinking the CIA is spying on you Hallucinations perceptions in the absence of external stimuli e.g. hearing sound when no sound is present Illusions misinterpretations of actual external stimuli e.g. hearing the wind blowing and thinking it is a bird chirping Loose associations ideas are presented with illogical or tenuous connections between them Hallucination types Visual hallucinations common in delirium more often a feature of medical rather than psychiatric illness Auditory hallucinations common in schizophrenia more common in psychiatric than medical disease Olfactory hallucinations often occurs as an aura of psychomotor epilepsy or brain tumors Gustatory hallucination rare Tactile hallucinations common in alcohol withdrawal e.g. formication - the sensation of ants crawling on one's skin also seen in cocaine abusers ("cocaine bugs") Hypnagogic hallucination occurs while going to sleep Hypnopompic hallucination occurs while waking from sleep