In psychiatry, hallucinations are defined as a perception experienced in the absence of an external stimulus to the corresponding sense organ. In simple terms, hallucinations are when people see, hear, feel, smell, or taste things that really don’t exist outside of their minds. For a hallucination to be considered as a true hallucination, it needs to have the following features:
- It seems to come outside of the mind.
- The hallucinations perceived, whether visual or auditory, need to be clearly demarcated. For example, if you have a visual hallucination of a certain person, he or she should be able to describe if the person was a female or male and what he/she was wearing. That means you should be able to explain the details of the hallucination you saw.
- It is experienced as a true perception.
If all of the above qualities are present, then it is considered as a true hallucination. If at least one quality is absent, then it is called as a pseudohallucination. Pseudohallucinations can occur in normal individuals and in people during situations of heightened emotions such as fear and anxiety.
Can true hallucinations occur in healthy people?
Yes, they do. There are two types of such hallucinations. They are:
- Hypnagogic hallucinations – occur when a person is falling asleep.
- Hypnopompic hallucinations – these occur when waking up from sleep.
However, these hallucinations are usually brief and simple (e.g., ringing bell or hears a name being called). The person usually wakes up suddenly and realized the nature of their experience; they do not regard it as a true perception.
What are the types of hallucinations?
Hallucination can occur in all sensory modalities, but those of hearing and seeing are the most frequent. The types of hallucinations are:
- Auditory hallucinations – hearing voices.
- Visual hallucinations - seeing things like animals, insects, or people.
- Tactile hallucinations – feeling as if someone is touching you or you are being tickled even if no one is around you. You may even feel insects crawling on your skin even when there is nothing to be seen.
- Olfactory hallucinations – smelling things.
- Gustatory hallucinations – feeling of an odd taste every time you eat or drink something.
What causes hallucinations?
Hallucinations are a common symptom in several psychiatric conditions. The most common cause of hallucinations is due to a condition known as schizophrenia. More than 70% cases of schizophrenia develop auditory hallucinations where they hear noises, voices, or music. Other causes of hallucinations include Parkinson’s disease, depression, mania, dementia, delirium, and substance abuse.
Brain tumors also can be another cause of hallucinations. The type of hallucination will depend on the location of the brain tumor.