A hallucination is the perception of images or sensations that are not actually present, usually arising due to disorder of the nervous system or in response to hallucinogenic substances. Hallucinations can occur through any of the senses including visual, auditory, gustatory, olfactory, and tactile sensory perceptions. Hallucinations may also be perceived through the nociceptive or proprioceptive senses, as in the hallucination of bugs crawling on top of or just under the skin while under the influence of LSD.
Some hallucinations are considered to be normal and healthy, such as hypnagogic and hypnopompic hallucinations, which are the sensational phenomena felt just before falling asleep or when waking up. Also, a mild or elementary hallucination is considered to be a disturbance, including hearing soft noises in the background or seeing images in one’s peripheral vision, like flashes or streaks of light, sparks, or blurry vision. These disturbances are momentary, lasting only seconds or a few minutes. An individual who is mourning the loss of a loved one or dealing with a traumatic experience may have occurrences of hallucinations, although these hallucinations are considered to be a normal coping mechanism.
Hallucinations are usually induced by the intake of alcohol or other substances including LSD, PCP, methamphetamine, heroin, marijuana, cocaine, or crack. Other drugs like prescription medications may induce hallucinations when seriously abused. Hallucinations may be experienced when becoming intoxicated or when coming down from a high. Some substance abusers actually seek drugs that induce these mind-altering experiences, such as LSD. Drug-induced hallucinations further distort an individual’s grasp of reality, which is very harmful for those who may already be struggling with low self-esteem, depression, anxiety, or other mental illnesses.
Some psychedelic drugs may eventually cause the abuser to experience what is known as a “bad trip” since the substance is directly affecting, slowing down, and/or damaging their metacognitive associations. During a “bad trip,” intense and disturbing emotional experiences are relived involving terror, trauma, or entrapment, or fears are made manifest.
Hallucinations may also experienced by those who suffer from such mental illnesses as schizophrenia, bipolar disorder, Alzheimer’s disease, psychotic depression, post-traumatic stress disorder, delirium tremens, or dementia. Hallucinations are also linked to cases of high fever, especially in children or older adults. Some individuals with a loss of perception, such as blindness or deafness, may also experience hallucinations. Additionally, hallucinations may be a symptom of a serious medical condition such as kidney failure, liver failure, or brain cancer. Other signs of a serious medical problem in conjunction with hallucinations include agitation, confusion, headaches, migraines, or vomiting.
Common hallucinations include hearing voices when no one has spoken; hearing music playing that is not present; seeing objects, beings, shapes, lights, colors, or patterns that are not present; fictionally seeing objects manipulate before one’s eyes; feeling false pain as if being attacked; or feeling a crawling sensation across the skin.
In some cases, the individual is aware that he or she is hallucinating, as in Charles Bonnet syndrome patients, narcoleptics, or people who have intentionally taken a hallucinatory substance. Lesions on the brain, especially on the brain stem or posterior temporoparietal, often cause some types of hallucinations, most often auditory hallucinations. In regard to mental illnesses, hallucinations are believed to be caused by a dysfunction of the neurotransmitters dopamine and glutamate. Psychological research has also proposed that malfunctions occurring with the brain’s metacognitive ability may cause the distortion of perceptions of reality with memories, thoughts, intentions, or beliefs, resulting in a hallucination.
If an individual begins hallucinating and appears to be incoherent, unresponsive, or “spaced out,” they have become detached from reality. These individuals should never be left alone during these times as their hallucinations may be indicative of an underlying serious mental condition or trauma. If left alone, the individual may become nervous, panicked, frightened, paranoid, and erratic. These individuals should receive immediate medical assistance either by contacting their health care physician, going to the emergency room, or by calling 911.