Auditory: Auditory hallucinations are by far the most common type and are most often caused by schizophrenia or other psychoses. An auditory hallucination (AH) is the false perception of sound, music, noises, or voices. Hearing voices when there is no auditory stimulus is the most common type of auditory hallucination in mental disorders. AH can be vague (humming or indistinguishable murmuring), fragmentary (words or phrases that are repeated such as "fag", "fat whore", "go to hell", or "get him"), or complex (hearing a voice or voices talking to an individual or talking about him/her or providing a running commentary about them. Typically voices are mocking, critical, condescending and disparaging. Often these voices warn the subject of perceived danger, including conspiracy theories that place him/her in imminent danger. Auditory hallucinations can also take the form of voices or other sounds which may or may not be distressing to the subject at all. In fact, 13% of individuals who experience AH find the voices to be soothing and calming. Auditory hallucinations may be experienced as coming from within one's body or from without. Voices heard outside one's own head are generally considered more severe. These voices can range from being amusing, to offensive, to controlling, or even commanding. The intensity, frequency and volume of auditory hallucinations are quite variable; soft or loud, continuous or infrequent. The subject may recognize the voice(s) as someone familiar or not at all.
Command Auditory Hallucinations: A command hallucination is when a voice tells an individual to carry out a specific act(s). A person experiencing this kind of hallucination frequently feels under a powerful obligation to carry out such actions. The results are often devastating. Approximately 30% of schizophrenics have command hallucinations in which they feel they must do what the voice tells them to do. Studies indicate between 22-58% (the best estimate is 40%) of these individuals report that they have complied with such commands. Statistically, over 50% of command hallucinations are to commit suicide, 10% for homicide, and 10% for some other non-lethal injury. Command hallucinations are a compelling predictor of violence. Suspects who experience command hallucinations to harm others are more than twice as likely to be violent. This risk is increased if the command voice is familiar, especially that of a close family member such as a parent.
Visual: A visual hallucination (VH) is a false perception of sight. VH are the second most common type of hallucination in psychotic disorders such as schizophrenia (24-72%). The content of the hallucination may be anything (such as shapes, colors, shadows, flashes of light) but are typically people or human-like figures. Disturbing examples include faces morphing in a mirror, corpses, the headline “Death” on every newspaper, vicious/wild animals, etc. Visual hallucinations are also commonly experienced in alcohol and drug related psychoses; seeing rats, snakes, insects, tiny people. Organic brain disorders (dementia), Parkinson’s disease, Charles Bonnet syndrome, sensory deprivation, cataracts, macular degeneration or glaucoma can also cause visual hallucinations. Sensory deprivation, hearing loss or deafness may also trigger auditory hallucinations.
Tactile: A tactile hallucination (TH) is a false perception or sensation of touch or of something happening in or on the body. The most common tactile hallucination is feeling like something is crawling under or on the skin, known as formication. Formication hallucinations are characteristic of cocaine/amphetamine intoxication, and alcohol/ benzodiazepines withdrawal. Other examples include tingling, burning, itching, feeling electricity through the body, and feeling a phantom limb after an amputation. Schizophrenics experiencing TH, frequently have comorbid paranoid delusions (machines or microchips planted by the government under the skin or the brain, skin itching from radioactivity beamed at them from a hostile source.). Tactile hallucinations are also seen in certain medical disorders; peripheral neuropathy, fever, Lyme disease, and skin cancer.
Gustatory: A gustatory hallucination is the false perception of taste. These hallucinations re experienced as strange tastes in something they are eating or drinking; pizza tasting like blueberries or meat tasting like bleach. Usually, the experience is unpleasant. For instance, an individual may complain of a persistent taste of metal, onions, etc. This type of hallucination is rare and is more commonly seen in some medical disorders (frontal lobe epilepsy, brain tumors, and migraines) than in mental disorders.
Olfactory: An olfactory hallucination is a false perception of odor or smell. Typically, the experience is very unpleasant. For example, the person may smell decaying fish, dead bodies, burning rubber, feces, rotting manure, or sulfur. The scent is frequently indescribable. Sometimes, those experiencing olfactory hallucinations believe the odor emanates from them. Olfactory hallucinations often accompany gustatory hallucinations and are more typical of medical disorders than mental disorders.
Treatment for Hallucinations
Hallucinations that are symptomatic of a mental illness should be treated by a psychiatrist. Anti-psychotic medications are effective in reducing and often eliminating hallucinations; Haldol, Thorazine, Clozaril, Risperdal, etc. When the hallucinations are part of a medical disorder, it is necessary to treat the underlying condition, remove the causative agent, and add antipsychotic medications.