Hallucination

A hallucination, in the broadest sense, is a perception in the absence of a stimulus. In a stricter sense, hallucinations are defined as perceptions in a conscious and awake state in the absence of external stimuli which have qualities of real perception, in that they are vivid, substantial, and located in external objective space. Some people have quick passing hallucination, particularly when falling asleep or waking up and this is considered normal. Hallucinations and delusions that persist or recur may be a sign of mental illness.

Hallucination is sometimes confused with Illusion and Delusion.

• Illusion - something not real or imaginary. An example is, a shadow of a curtain taken for a person.

• Delusion - is a mistaken belief that cannot be corrected by reasoning. An example is, a person may think that a dear friend is trying to kill him.

Types

Types of Normal Hallucination :

• Hypnagogic hallucination - happens when a person is falling asleep. Usually last from seconds to minutes.
• Hypnopompic hallucination - happen when one is waking up.

Hallucinations are categorized according to which sensory modality is involved and, in addition, are categorized as either mood-congruent or mood-incongruent. The types of hallucinations are:

• Auditory: 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. The voice may be heard either inside or outside one’s head and is generally considered more severe when coming from outside one’s head. The voices may be male or female, recognized as the voice of someone familiar or not recognized as familiar, and may be critical or positive. In mental disorders such as schizophrenia, however, the content of what the voices say is usually unpleasant and negative. In schizophrenia, a common symptom is to hear voices conversing and/or commenting. When someone hears voices conversing, they hear two or more voices speaking to each other (usually about the person who is hallucinating). In voices commenting, the person hears a voice making comments about his or her behavior or thoughts, typically in the third person (such as, "isn’t he silly"). Sometimes the voices consist of hearing a "running commentary" on the person’s behavior as it occurs ("she is showering"). Other times, the voices may tell the person to do something (commonly referred to as "command hallucinations").
• Gustatory: A false perception of taste. Usually, the experience is unpleasant. For instance, an individual may complain of a persistent taste of metal. This type of hallucination is more commonly seen in some medical disorders (such as epilepsy) than in mental disorders.
• Olfactory hallucination: A false perception of odor or smell. Typically, the experience is very unpleasant. For example, the person may smell decaying fish, dead bodies, or burning rubber. Sometimes, those experiencing olfactory hallucinations believe the odor emanates from them. Olfactory hallucinations are more typical of medical disorders than mental disorders.
• Somatic/tactile hallucination: A false perception or sensation of touch or something happening in or on the body. A common tactile hallucination is feeling like something is crawling under or on the skin (also known as formication). Other examples include feeling electricity through one’s body and feeling like someone is touching one’s body but no one is there. Actual physical sensations stemming from medical disorders (perhaps not yet diagnosed) and hypochondriacal preoccupations with normal physical sensations, are not thought of as somatic hallucinations.
• Visual hallucination: A false perception of sight. The content of the hallucination may be anything (such as shapes, colors, and flashes of light) but are typically people or human-like figures. For example, one may perceive a person standing before them when no one is
• there. Sometimes an individual may experience the false perception of religious figure (such as the devil, or Christ). Perceptions that would be considered normal for an individual’s religion or culture are not considered hallucinations.
• Mood-congruent hallucination: Any hallucination whose content is consistent with either the depressive or manic state the person may be in at the time. Depressive themes include guilt, death, disease, personal inadequacy, and deserved punishment. Manic themes include inflated self-worth, power, knowledge, skills, and identity and a special relationship with a famous person or deity. For example, a depressed person may hear voices saying that he or she is a horrible person, whereas a manic person may hear voices saying that he or she is an incredibly important person.
• Mood-incongruent hallucination: Any hallucination whose content is not consistent with either the depressed or manic state the person is in at the time, or is mood-neutral. For example, a depressed person may experience hallucinations without any themes of guilt, death, disease, personal inadequacy, or deserved punishment. Similarly, a manic person may experience hallucinations without any themes of inflated self-worth, power, knowledge, skills, or identity or a special relationship to a famous person or deity.

Causes of Hallucination:

• It may be induced by drugs (hallucinogenic drugs) or hypnosis
• It may be due to lack of sleep
• Depression
• Mental Illness

Scientific explanations

Various theories have been put forward to explain the occurrence of hallucinations. When psychodynamic (Freudian) theories were popular in psychiatry, hallucinations were seen as a projection of unconscious wishes, thoughts and wants. As biological theories have become orthodox, hallucinations are more often thought of (by psychologists at least) as being caused by functional deficits in the brain. With reference to mental illness, the function (or dysfunction) of the neurotransmitter dopamine is thought to be particularly important.^[12] The Freudian interpretation may have an aspect of truth, as the biological hypothesis explains the physical interactions in the brain, while the Freudian deals with the origin of the flavor of the hallucination. Psychological research has argued that hallucinations may result from biases in what are known as metacognitiveabilities.^[13] These are abilities that allow us to monitor or draw inferences from our own internal psychological states (such as intentions,memories, beliefs and thoughts). The ability to discriminate between internal (self-generated) and external (stimuli) sources of information is considered to be an important metacognitive skill, but one which may break down to cause hallucinatory experiences. Projection of an internal state (or a person's own reaction to another's) may arise in the form of hallucinations, especially auditory hallucinations. A recent hypothesis that is gaining acceptance concerns the role of overactive top-down processing, or strong perceptual expectations, that can generate spontaneous perceptual output (that is, hallucination

Stages of a hallucination

1. Emergence of surprising or warded-off memory or fantasy images 
2. Frequent reality checks 
3. Last vestige of insight as hallucinations become "real" 
4. Fantasy and distortion elaborated upon and confused with actual perception 
5. Internal-external boundaries destroyed and possible panentheistic experience 

When to Contact a Medical Professional   

A person who begins to hallucinate and is detached from reality should get checked by a health care professional right away, because many medical conditions that can cause hallucinations may quickly become emergencies. A person who is hallucinating may become nervous, paranoid, and frightened, and should not be left alone.

Call your health care provider, go to the emergency room, or call the local emergency number (such as 911) if someone appears to be hallucinating and is unable to tell hallucinations from reality.

What to Expect at Your Office Visit   

The health care provider will do a physical examination and take a medical history. Blood may be drawn for testing.

Medical history questions may include the following:

• Do you hear a voice?
• Do you see something?
• Do you have a sensation of feeling something or being touched?
• How long have you been having hallucinations?
• When did the hallucinations first appear?
• Do the hallucinations occur just before or after sleep?
• Has there been a recent death or other emotional event?
• What medications are you taking?
• Do you use alcohol regularly?
• Do you use illegal drugs?
• Are the hallucinations related to a traumatic event?
• Is there agitation?
• Is there confusion?
• Is there a fever?
• Is there a headache?
• Is there vomiting?