Hallucinations are false sensory perceptions that are unrelated to outside events. Essentially, a hallucination is seeing, hearing, tasting, feeling, or smelling something that does not exist while a person is awake and conscious.
Have you ever experienced a physical feeling (floating, falling, paralyzed), a smell or taste (chocolate, bacon, maple syrup), a sound (your name being called, a doorbell ringing), or seen images (random speckles, lines, tunnels of light, geometrical patterns), as you are falling asleep or before awakening? These vivid sensations are known hypnopompic or hypnogogic states. They are not uncommon or dangerous, and they are not considered true hallucinations if you are not awake. However, they do set up a framework to understand what it feels is like to hallucinate.
Hallucinations can be amusing and/or pleasant, annoying and/or frightening. Hallucinations can also lead to violence, suicide and homicide. Take the case of an English serial killer, Peter Sutcliffe (The Yorkshire Killer), who in 1981was convicted of murdering thirteen women because loud hallucinations had instructed him to kill them. Sutcliffe believed he was the instrument of God’s wrath on earth and waged a holy war against immorality. His delusional system centered on the belief that God had given him a mission to rid the world of prostitutes.
The primary sensory hallucinations that individuals experience are auditory (hearing voices when no one has spoken), visual (seeing something that isn’t there), or tactile (feeling a crawling sensation on the skin). Hallucinations related to smell or taste are rarer. Some people experiencing hallucinations may be aware that the perceptions are false; whereas others may truly believe that what they are seeing, hearing, tasting, feeling, or smelling is real.
Hallucinations should not be confused with illusions or delusions. Hallucinations are false sensory perceptions of things that are not there. Illusions are misperceptions of sensory things that are in fact there. Delusions are deeply fixed beliefs maintained by an individual despite contradictory information or evidence. Individuals who experience auditory hallucinations frequently also have a paranoid delusional disorder.
Common Causes of Hallucinations
There are numerous medical and psychiatric causes of hallucinations. Hallucinations have been a hallmark of mental illness throughout time. They may be present in any of the following mental disorders: psychotic disorders, bipolar disorder, psychotic depression, PTSD, delirium, or dementia. Up to 75% of schizophrenic patients admitted for treatment report hallucinations.
Hallucinations can be symptoms of medical or neurological disorders; liver failure, kidney failure, AIDS, brain cancer, Parkinson’s disease, strokes, tumors, fever and seizures. Or they can be symptoms of sensory disorders such as blindness and deafness.
Additionally, the use of certain recreational drugs may induce hallucinations: amphetamines, cocaine, hallucinogenics (ecstasy, LSD, psilocybin), PCP, steroids, and certain potent types of marijuana. Withdrawal from alcohol, sedatives, narcotics, hypnotics, or anxiolytics can also cause hallucinations. Occasionally, after repeated ingestion of drugs, some people experience "flashbacks"; spontaneous visual hallucinations during a drug free state, often months or years later.
Hallucinations can occur in people who are not mentally or physically ill. Sensory, sleep, food, and water deprivation can produce hallucinations. Transitioning from sleep to wakefulness and vice versa can also result in hallucinations. In some cases, hallucinations may be normal. For example, hearing the voice of, or briefly seeing, a loved one who has recently died can be a part of the grieving process.
Types of Hallucinations: