Amnesia or memory loss is defined as unusual forgetfulness where the loss of memory is greater than ordinary circumstances. The memory loss can be temporary or permanent. In severe cases, memory impairment may interfere with daily activities.
The most common types of amnesia include:
| Types | How it affects |
| Anterograde amnesia | It is most commonly caused by head trauma. A person cannot remember recent information, although they can remember old information and events that happened much prior to the injury. Damage to the brain results in the inability to transfer recent events into long-term memory. Anterograde amnesia affects a person’s quality of life because day-to-day functional memory is poor. This condition can also create safety issues at work and on roads. |
| Retrograde amnesia | It is the loss of the ability to recall episodic memories and past events that occurred prior to the head trauma. People with retrograde amnesia may have complete or partial memory loss depending on the extent of the damage. Retrograde amnesia affects the memories of events in the recent past more than those in the distant past. |
| Transient global amnesia (TGA) | It is typically a temporary loss of memory and is more prevalent in adults older than the age of 50 years. The person is usually unable to recall events that have occurred a few minutes ago. It may be due to age-induced changes in the brain. |
| Dissociative amnesia/Psychogenic amnesia | It is temporary amnesia characterized by episodic memory loss that may last for hours or days or even years. The psychological trauma may cause a temporary blackout state, and a person is usually unable to recall their personal information or identity. This type of amnesia is caused by psychological reasons triggered by an extremely traumatic event that the person is unable to cope with (rape, attempt on life, etc.). The ability to remember usually returns, but the memory of the shocking event may never return completely. |
| Traumatic amnesia | This type of amnesia occurs because of a trauma or an injury to the head caused by an automobile accident, a strike on the head, fall from a height, etc. The extent of memory loss depends on the degree of trauma and might be temporary or permanent. |
| Drug-induced amnesia: | This is short-term amnesia caused by some drugs such as benzodiazepines that interfere with the memory formation process in the brain. The person is unable to recall events that occurred when under the influence of the drug. The memory restores once the effect of the drug wears off. |
| Korsakoff’s syndrome psychosis | Korsakoff’s syndrome occurs in long-term alcoholics and people with severe malnutrition due to thiamine deficiency (vitamin B1). This disease is characterized by the occurrence of both anterograde and retrograde amnesia. Short-term memory of the person is not affected, but there may be difficulty in recalling past events. Immediate memory is also affected. |
| Selective amnesia | People forget certain parts of their memory or certain events that have occurred in their life. This type of amnesia is often used for treatment in psychiatry. Selective amnesia is induced by electroconvulsive therapy (ECT) to make people forget certain distressful events that are triggers for depression, extreme anxiety, or phobias. |
| Infantile amnesia | A person is unable to recall events from their early childhood. This condition was attributed to language development problem or caused by memory areas of the brain not fully maturing during childhood. |
| Epileptic amnesia | This type of memory loss is rare and is found in people having temporal lobe epilepsy. It is also seen in people with epilepsy as a response to some anti-epilepsy drugs. |
| Posthypnotic amnesia | People do not recall events that occurred during hypnosis. This is used as a therapy to treat many psychiatric illnesses. |
| Source amnesia | The person can remember information but not how they got that information. |
| Blackout phenomenon | Heavy drinking can leave a person with memory gaps during a drinking binge. |
What are the signs and symptoms of amnesia?
Common amnesia symptoms depend on the type of amnesia and include the following:
- Forgetfulness
- Memory loss
- Confusion
- Inability to recognize faces and places
- Inability to process or store new information or memories
- Generation of false memories
- After recovery, people have no memory of their amnesia episode
What are the causes of amnesia?
Amnesia can be caused by a wide range of conditions, including:
- Head injury
- Brain damage (especially the hippocampus area in the brain)
- Brain tumor
- Brain surgery
- Concussion or a head trauma
- Lack of oxygen to the brain for too long (drowning)
- Brain infections (encephalitis, Lyme disease, syphilis, human immunodeficiency virus/acquired immunodeficiency syndrome [HIV/AIDS])
- Transient ischemic attack (TIA) or a stroke
- Hydrocephalus (fluid collection in the brain) due to multiple causes
- Parkinson disease or Huntington disease
- High fever and seizures
- Epilepsy
- Emotional shock or hysteria
- Alzheimer's disease and dementia
- Bipolar disorder
- A traumatic or stressful event
- Depression or mental health disorders such as schizophrenia
- Electroconvulsive therapy (ECT)
- Hypothyroidism
- Cancer treatment
- Excessive alcohol use
- Vitamin B1 or vitamin B12 deficiency
- Medications (general anesthesia and benzodiazepines)
- Certain drugs such as barbiturates or heroin
How is amnesia treated?
In most cases, amnesia resolves itself without treatment. Family support, psychotherapy, hypnosis, photographs, smells, and music may help restore memory. Treatment may be necessary if there is physical or mental disorder.
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