Amnesia: Types, Tests, Diagnosis, Symptoms & Causes

Amnesia is a memory disorder whereby people find it difficult to remember past experiences, form new memories, or both.

People with amnesia may find it hard to recall memories such as facts, information, and experiences, but they may also have difficulty memorizing new information and imagining the future.

Being a little forgetful sometimes is different from amnesia. Similarly, mild memory loss as a natural part of aging is considered normal.

Significant memory loss or the inability to form new memories, however, may indicate the presence of an amnesic disorder. Amnesia is also not the same as dementia or other degenerative disorders.

Dementia is a disease that causes degenerative memory loss, as well as those with the disease suffering from other cognitive issues that do not occur in those with amnesia.

There is often a misconception about amnesia, especially present in movies, where people with amnesia are shown to forget their whole identity.

However, those with amnesia usually retain the knowledge of their own identity, as well as having their motor skills intact. In many cases of amnesia, the memory loss is temporary and will return to normal after a while, but in others, the memory loss can be permanent.

How does memory work?

There are three known types of memory:

  • Short-term memory (STM, also known as working memory) – these are thoughts that are temporary, usually lasting between 10-30 seconds. The frontal and parietal lobes of the brain are mostly responsible for STM.

  • Long-term memory (LTM) – thoughts that last beyond a minute or longer become an LTM. This is usually when the STM has been paid attention to so it can be processed deeper. The hippocampus and the temporal lobes are responsible for LTM. There are two types of LTM: implicit (procedural) and explicit (declarative).

  • Sensory memory – this type of memory lasts for less than a second. This includes visual, auditory, and tactile sensory input that is briefly attended to and mostly forgotten or is passed on for further processing.

Four processes are involved in memory: encoding, consolidation, storage, and retrieval.

All of these processes determine whether something is remembered or forgotten:

  • Encoding – occurs in the prefrontal cortex; this is when the brain decodes new information. The information or experience is broken down into manageable parts for the rest of the brain to use.

  • Consolidation – occurring in the hippocampus, this is where the encoded information is linked to existing memories. This helps to determine where the new information belongs and solidifies the memory.

    Consolidating memories organizes everything in a way that will make it easier to recall in the future.

  • Storage – this takes place throughout the cortex; this is when the brain stores the information. The information that gets associated with existing memories gets preserved and retained. In contrast, the less important information gets edited out for the memory to stay focused on what is most important.

  • Retrieval – occurs in the prefrontal cortex, hippocampus, and cortex; this is when the brain reactivates the information for use in the future.

    During the retrieval process, the brain runs through encoding, consolidation, and storage of the memory repeatedly. With each run-through, retrieval gets easier.

    The retrieval stage protects memories from being lost. The oldest and most retrieved memories are the most resilient.


There are two main features of amnesia. Someone may have difficulty learning new information following the onset of amnesia, or they may have difficulty remembering past events and information previously familiar to them.

The symptoms of amnesia depend on the type of amnesia being experienced. Some of the common experiences of someone with amnesia are as follows:

  • Difficulty with recalling facts, events, places, and specific details

  • An impaired ability to learn new information

  • Confusion

  • An inability to recognize locations or faces

  • Confabulation, in which the brain subconsciously invents false memories to fill in gaps in memory

  • Uncoordinated movements and tremors may indicate neurological problems

  • Disorientation

  • Partial or total loss of memory

Most people with amnesia have problems with their short-term memory. This means that they cannot retain new information, with recent memories most likely to be lost.

In contrast, their long-term memories can remain intact, those being more deeply ingrained memories of the individual.

For instance, someone may be able to recall experiences from childhood or remember significant events from history but not be able to know what month it was or what they last ate.

Amnesia does not mean that a person’s intelligence, general knowledge, attention, personality, sense of identity, or awareness is affected.

They will usually still retain their previously learned skills, such as understanding language, riding a bike, or playing an instrument. People with amnesia may also understand that they are suffering from memory problems.


There are many different types of amnesia that a person may have. Below are some of the most common ones:

Anterograde amnesia

If someone has anterograde amnesia, they cannot remember new information. The person can remember information and events that have happened before the onset of amnesia, but things that happened more recently and information that should be stored in STM disappear.

The effect of this type of amnesia can be temporary, such as when experiencing a blackout from consuming too much alcohol. It can also be permanent if the hippocampus becomes damaged, an area of the brain that plays a significant role in forming memories.

This type of amnesia is usually due to an error in the encoding or consolidation of the process of memory. When an event cannot be encoded or consolidated in the short term, it makes it harder for the brain to store this information and process it for long-term retrieval in the future.

Retrograde amnesia

In contrast to anterograde amnesia, someone with retrograde amnesia will be unable to remember old memories. In this instance, they cannot remember the events that occurred before the onset of their amnesia, but they can remember what happened afterward. They will essentially lose their existing, previously made memories.

This type of amnesia tends to affect the most recently formed memories first, so the events immediately leading up to the onset of amnesia will likely be forgotten first. In contrast, older memories, such as those from childhood, are usually affected more slowly.

Retrograde amnesia usually occurs due to a problem in the storage or retrieval stage of the memory process. Conditions such as dementia can cause gradual retrograde amnesia.

In rare cases, both retrograde and anterograde amnesia can occur together, so someone will lose their existing memories and be unable to form new memories.

Transient global amnesia

Transient global amnesia is when someone has a temporary loss of all memory and, in severe cases, difficulty forming new memories.

This type of amnesia is very rare and is likely to occur in older adults with vascular disease. It is a sudden and temporary memory loss lasting between one to ten hours.

When experiencing transient global amnesia, a person cannot make new memories or recall events during the period of amnesia. They can remember deeply ingrained information such as who they are and who their family is but are often unaware of where they are, and what day, time, or month it is.

They can experience a lot of confusion and agitation that comes and goes repeatedly over the course of several hours.

Traumatic amnesia

Someone experiencing traumatic amnesia suffers memory loss due to a hard blow to the head. They may have difficulty remembering events from minutes to hours ago, feel disorientated to time and where they are, and they may not understand what has happened to them.

The person may experience a brief loss of consciousness or a coma before the amnesia. If someone experiences amnesia after trauma to the head, this may indicate that they have a concussion. Sometimes, amnesia is a normal part of the recovery process following head trauma.

Amnesia from trauma to the head is usually temporary, but how long it lasts depends on the injury’s severity. However, in some cases, traumatic amnesia can become permanent depending on the severity of the injury.

Dissociative amnesia

Dissociative amnesia is a type of dissociative disorder, a condition that affects the consciousness, awareness, and perception of a person. In some instances, this can be limited to a specific area, but in more severe cases, a person may forget almost all their identity or take an entirely new identity.

The onset of dissociative amnesia is usually sudden and may last for minutes, hours, or days, with rarer cases lasting for months or years. People usually develop this type of amnesia after experiencing a very stressful or traumatic experience as a way to cope with the situation.

Although the ability to remember usually returns, the memory of the shocking event which caused the amnesia may never come back completely.

Infantile amnesia

Infantile amnesia is when an adult cannot remember the first few years of life as a baby or a toddler. Most people cannot remember their first 3-5 years of life, making this a very common type of amnesia.

This inability to remember early life could be due to language not being fully developed yet, or some memory areas of the brain not being mature enough.


There are many causes of amnesia, but most fall into two categories: neurological and functional causes.


Neurological amnesia is caused by various brain diseases, injuries, infections, or other medical conditions. Other causes of this type of amnesia include:

  • Stroke

  • Brain inflammation

  • Lack of oxygen to the brain, e.g., from a heart attack or respiratory distress

  • Long-term alcohol abuse

  • A vascular disease that has been known to cause transient global amnesia

  • Tumors in the areas of the brain that control memory

  • Degenerative diseases such as Alzheimer’s disease

  • Seizure activity

  • Certain medications, such as benzodiazepines or other medications that have a sedative effect

Normal memory function involves many parts of the brain, so any disease or injury that affects the brain can also affect memory. Damage that occurs to the limbic system, an area of the brain that controls emotions and memories, specifically the hippocampus, may be a possible cause for amnesia developing in many people.

Anterograde amnesia typically results from damage to the prefrontal cortex or the hippocampus. In contrast, retrograde amnesia typically results from damage to the cortex but could involve the prefrontal cortex or hippocampus as well.

Since the hippocampus plays a big role in forming memories, organizing them, and retrieving them when needed, any damage to this area is detrimental as it limits these functions.

The hippocampus cells are also thought to be some of the most energy-hungry and fragile. Thus, they are most easily disrupted by low oxygen levels and other threats such as toxins. It is believed that if the hippocampus is damaged in both hemispheres of the brain, the person could develop complete anterograde amnesia.

Electroconvulsive therapy (ECT) has also been shown to cause some amnesia as a side effect of the treatment. ECT is usually used as a treatment for depression or other conditions where the person isn’t responding to other types of treatment.

This involves inducing seizures in specific brain regions for therapeutic effect. However, some people may experience retrograde amnesia in the weeks or months before the treatment. They could also experience anterograde amnesia, usually resolving within a few weeks of treatment.


Functional causes of amnesia are usually related to psychiatric or emotional trauma. Functional amnesia also usually only causes retrograde amnesia and doesn’t affect the ability to form new memories, although in severe cases, people with functional trauma can forget who they are.

Dissociative amnesia stems from emotional shock or trauma, such as experiencing or being the victim of a violent crime or experiencing or being the victim of emotional, physical, or sexual abuse.

With this type of amnesia, the person’s mind rejects thoughts, feelings, or information that they are too overwhelmed to handle. They may briefly forget the trauma they went through, either briefly or long-term.

Any type of intolerable life situation can cause severe psychological stress and internal conflict that can lead to some degree of amnesia.

This stress is more likely to disrupt personal and historical memories rather than interfere with making new memories.


To diagnose amnesia, doctors usually complete a comprehensive evaluation to rule out other possible reasons for memory loss.

The doctor will want to rule out conditions such as Alzheimer’s, other forms of dementia, depression, or a brain tumor.

The evaluation may begin by completing a thorough medical history of the individual. As the person with suspected amnesia may not be able to provide all the necessary details, a family member or someone who knows the person well will generally take part in the interview too.

The doctor will ask many questions to understand memory loss. Some of the issues to address include the following:

  • Understanding the type of memory loss – including whether it is a recent problem or long-term.

  • When the memory problem started and how they may have progressed.

  • What could have been the possible cause for the memory loss, e.g., head trauma.

  • A discussion of family medical history, especially of neurological diseases.

  • Whether the person uses drugs or drinks alcohol.

  • Other signs and symptoms are experienced, such as confusion, language problems, or personality changes.

  • Whether the person has a history of headaches, seizures, or depression.

The examination should also include a physical exam to check the person’s reflexes, sensory function, balance, and any other aspects that may be necessary.

Cognitive tests will also be completed by the doctor to check the person’s thinking, judgment, and short-term and long-term memory. For instance, they may be asked about past events, given general knowledge questions, or asked to repeat a list of words.

This can help determine the extent of the memory loss and provide insights into what kind of treatment the person may need.

The doctor may also arrange for diagnostic tests to investigate memory loss further. This can include tests such as:

  • Imaging tests such as magnetic resonance imaging (MRI) and computerized tomography (CT) scans to check for brain damage or abnormalities.

  • Blood tests to check for infection, nutritional deficiencies, or other issues.

  • An electroencephalogram (EEG) is used to check for seizure activity.


Treatment for amnesia depends on the type of amnesia being experienced and what caused the memory problems.

With many types of amnesia, no treatment is necessary as it is likely that memory will return to normal in a short amount of time.

For instance, amnesia from mild head trauma may resolve within minutes or hours. Amnesia from a severe head injury may last a bit longer, for up to a week. In rarer cases, amnesia from a severe head injury may last for months.

Chemically induced amnesia from alcohol can be resolved through detoxication. Once this is out of the system, the memory problems of the person will probably subside.

Suppose amnesia is caused as a side effect of medications such as benzodiazepines or other medications with a sedative effect. In that case, the medications could be gradually reduced, or the dosage can decrease only with the advice given by a doctor.

It could be that a discussion of a person’s medicative treatment plan is required to weigh up the advantages and disadvantages of taking medication that is causing amnesia.

Amnesia caused by neurological disease or infection will require treatment for the underlying medical cause of the amnesia. Once the medical issue is treated, this should also reduce memory problems. Amnesia, which is derived from dementia, is often incurable.

However, a doctor may prescribe medications to support learning and memory for these individuals, such as donepezil, galantamine, or rivastigmine.

As most functional amnesia results from emotional trauma, it may be useful to find a way to deal with the traumatic events in a safe way. The best therapy will usually depend on the individual and what caused the amnesia. Hypnosis can be an effective therapy for recalling memories that have been forgotten.

For many, the memory that has been forgotten may be too painful to rediscover. Instead, it may be recommended to find a therapy that focuses on strategies to help make up for the memory problem and cope with additional negative thoughts surrounding the cause of the amnesia.

People may wish to undergo any of the following therapies:

  • Cognitive behavioral therapy (CBT)

  • Family therapy

  • Art or music therapy

  • Meditation or mindfulness training

  • Other types of psychotherapy

Many people with amnesia may find that occupational therapy is the most useful for them if they have persistent memory loss. A person may work with an occupational therapist to learn new information to replace what may have been lost or use intact memories as a basis for taking in new information.

Memory training may also include different strategies for organizing information so that it is easier to remember. The therapist can also teach the person how to use memory aids for organizing information so it can be more effectively retrieved.

They may also suggest using digital aids, such as smartphones, to help with daily tasks and set reminders about important events or when to take their medication, for instance.


In many cases, amnesia is not preventable. However, there are some ways to keep the mind active and the brain protected, especially when getting older, which could prevent age-related memory loss:

Diet and physical exercise

Eating a diet with lots of nutrients and vitamins, as well as exercising regularly, could help to keep the brain healthy. Exercise, especially aerobic exercise, has been suggested to be linked to improved memory and thinking skills.

This may be due to more blood being pumped around brain regions that specifically improve memory and mental sharpness (Guadagni et al., 2020).

Aside from food, staying hydrated is important as it is suggested that even mild dehydration can adversely affect brain functioning and cause cognitive decline (Pross, 2017).

Staying mentally active

While it is important to keep physically active, keeping the mind active may also help to prevent memory loss.

This can include reading books or playing mind-stimulating games. Activities that involve mental effort, like problem-solving or using imagination, can help stimulate the mind.

Quality sleep

It has been suggested that a lack of sleep can impair a person’s ability to focus and learn efficiently and that sleep is necessary to consolidate a memory so that it can be recalled in the future (Marks, 2021).

Therefore, sleep may be crucial for the brain’s ability to learn and remember, so ensuring a regular sleep pattern and getting plenty of sleep may help to prevent memory loss in the future.

Managing stressors

Stress can affect how memories are formed, such as finding it more difficult to create short-term memories and turning those into long-term memories. Also, during periods of stress, one is less likely to remember details of the event later accurately.

Therefore, managing stressors in life could help to prevent problems with memory. This can include good sleep and physical activity, as mentioned above, but it can also include breathing exercises, mindfulness, or cutting unnecessary known stressors from life.

Protecting the head

Since damage to the brain can cause amnesia, protecting the head wherever possible can help prevent amnesia associated with brain trauma. Some preventions for head trauma include:

  • Wearing protective headgear when cycling and motorcycling.

  • Wearing a seatbelt in the car.

  • Avoiding excessive alcohol drinking so that balance is less likely to be lost.

  • Getting eye check-ups annually to help prevent dizziness that can result in falls.

  • Ask the doctor about any prescribed medications and whether they may cause dizziness.


Guadagni, V., Drogos, L. L., Tyndall, A. V., Davenport, M. H., Anderson, T. J., Eskes, G. A., Longman, R. S., Hill, M. D. & Poulin, M. J. (2020). Aerobic exercise improves cognition and cerebrovascular regulation in older adults. Neurology, 94(21), e2245-e2257.

Pross, N. (2017). Effects of dehydration on brain functioning: a life-span perspective. Annals of Nutrition and Metabolism, 70(Suppl. 1), 30-36.

Saul Mcleod, PhD

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Educator, Researcher

Saul Mcleod, Ph.D., is a qualified psychology teacher with over 18 years experience of working in further and higher education.

Olivia Guy-Evans

Associate Editor for Simply Psychology

BSc (Hons), Psychology, MSc, Psychology of Education

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.