Memory loss (amnesia)

A person’s ability to recall events and experiences involves a variety of complex brain processes. Researchers still do not understand exactly what happens when a person commits something to memory or retrieves information stored in the brain.

When a person develops amnesia, they often lose memories of important milestones, key events or people in their life, and vital facts they have learned.

Most people with amnesia are lucid and have a sense of self. In some cases, they may have full memories up to a certain point in time but have difficulty remembering things afterward. In other cases, they will lose memories from before a point in time. More often, the memory loss is patchy, with a person losing memories of certain events.

Some people with amnesia find it hard to imagine the future. This is because the human brain constructs future scenarios based on its recollections of past experiences.

Several different conditions involve amnesia, and there are many types of amnesia. Some features of different types of amnesia can overlap, and a person can have more than one type. Amnesia can be temporary or long lasting.

The most common types of amnesia are:

• Anterograde amnesia: A person with anterograde amnesia cannot remember new information. This usually results from brain trauma, such as a blow to the head that causes brain damage. The person will have their full memory from the time before the injury.
• Retrograde amnesia: In some ways the opposite of anterograde amnesia, retrograde amnesia is when a person cannot remember events that occurred before their trauma, but they can remember what happened after it. In rare cases, both retrograde and anterograde amnesia can occur together.
• Transient global amnesia: This is a temporary loss of all memory and, in severe cases, difficulty forming new memories. This is very rare and more likely in older adults with vascular (blood vessel) disease.
• Traumatic amnesia: This refers to memory loss resulting from a hard blow to the head, for instance, in a car accident. The person may experience a brief loss of consciousness or coma. This type of amnesia is usually temporary, but its duration often depends on the severity of the injury. Amnesia can be an important indicator of concussion.
• Fugue or dissociative amnesia: Rarely, a person can forget both their past and their identity. They may wake up and suddenly have no sense of who they are. The trigger is usually a traumatic event. The ability to remember commonly returns within minutes, hours, or days, but the memory of the triggering event may never come back completely.
• Posthypnotic amnesia: A person cannot recall what occurred while they experienced hypnosis.
• Source amnesia: A person can remember certain information but not how or where they got it.
• Alcohol-induced amnesia: Also called a blackout, this is when a bout of heavy drinking leaves a person with memory gaps.
• Prosopamnesia: The person cannot remember faces. People can either acquireTrusted Source it or be born with it.

Another type of amnesia is childhood amnesia, or infantile amnesia. However, this is not an actual disorder. A young child’s language and memory are still developing. As a result, most adults cannot recallTrusted Source events from early childhood.

Any disease or injury that affects the brain can interfere with memory. Memory function engages many different parts of the brain simultaneously.

Damage to brain structures that form the limbic system, such as the hippocampus and thalamus, can lead to amnesia. The limbic system controls a person’s emotions and memories.

Medical causes

Amnesia may result from brain injury or damage. Possible causes include:

• stroke
• illnesses that cause encephalitis, or brain inflammation, which typically include bacterial or viral infection or autoimmune reaction
• oxygen deprivation, which may result from a heart attack, respiratory distress, or carbon monoxide poisoning
• some medications, such as the insomnia drug Ambien
• subarachnoid hemorrhage, or bleeding in the area between the skull and the brain
• a brain tumor that affects a part of the brain involved in memory
• some seizure disorders
• head injuries, which can lead to loss of memory that is usually temporary
• surgery and anesthesia, which may cause a person to have trouble remembering what happened right before or after the procedure

Wernicke-Korsakoff syndrome, a condition caused by extended alcohol misuse or thiamin (vitamin B1) deficiency, can lead to progressive memory loss that worsens over time. It can also lead to neurological problems, such as poor coordination and loss of feeling in the toes and fingers.

Psychological amnesia

Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM–5) lists amnesia as a type of dissociative disorder. This usually refers to anterograde or retrograde amnesia caused by psychological trauma or stress without the presence of any physical cause.

Examples of dissociative conditions that can present with amnesia include:

• dissociative fugue
• dissociative identity disorder
• post-traumatic stress disorder (PTSD)
• acute stress disorder

Contributing traumatic causes or triggers can include:

• experiencing violent crime or a terrorist attack
• being sexually, physically, or emotionally abused
• experiencing trauma while serving in the military
• surviving a natural disaster

Any intolerable life situation that causes severe psychological stress and internal conflict can lead to some degree of amnesia. Psychological stressors are more likely to disrupt personal, historical memories rather than interfere with forming new memories.

The following are common symptoms of different types of amnesia:

• impaired ability to learn new information (anterograde amnesia)
• impaired ability to remember past events and previously familiar information (retrograde amnesia)
• experiencing false memories, which are either completely invented memories or real memories misplaced in time — a phenomenon knownTrusted Source as confabulationTrusted Source
• impaired short-term memory
• partial or total loss of all memory
• confusion

A doctor will need to rule out other possible types of memory loss, including those caused by dementia, Alzheimer’s disease, depression, or a brain tumor.

The doctor will take a detailed medical history, which may be difficult if the person does not remember. Family members or caregivers may need to be present.

The doctor will need the person with amnesia’s permission to talk about their medical details with somebody else.

Questions may include:

• Can the person remember recent events and events further back in time?
• When did the memory problems start?
• How did they develop?
• Could any factors have caused the memory loss, such as a head injury, surgery, or stroke?
• Is there a family history of any neurological or psychiatric conditions?
• Does the person consume alcohol?
• Are they taking any medication?
• Have they taken illegal drugs, such as cocaine or heroin?
• Are the symptoms undermining their ability to look after themselves?
• Do they have a history of depression or seizures?
• Have they ever had cancer?

The doctor will also do a physical exam that might include checking certain brain and nervous system functions, such as:

• reflexes
• sensory function
• balance

The doctor may also check the person’s:

• judgment
• short-term memory
• long-term memory

The memory assessment will help determine the extent of memory loss. This will help find the best treatment.

To find out whether there is any physical damage or brain abnormality, the doctor may order an MRI, CAT scan, or electroencephalogram (EEG).

Blood tests may reveal the presence of any infection or nutritional deficiencies.

In many cases, amnesia resolves without treatment. However, if an underlying physical or mental disorder is present, treatment for that condition may be necessary.

Psychotherapy or cognitive behavioral therapy (CBT) may help some people with amnesia. Hypnosis can be an effective way of recalling forgotten memories. Working on retrieving memories and managing psychological issues that may have contributed to amnesia are important aspects of any amnesia treatment.

Meditation and related mindfulness activities may help a person relax the mind, which may help retrieve forgotten memories.

Family support is also crucial. Showing the person photographs of past events, exposing them to familiar smells, and playing familiar music may help.

There are currently no drugs available for restoring memory lost due to amnesia. However, there are treatments for the underlying causes.

For example, Wernicke-Korsakoff syndrome (WKS) can involve memory loss due to a thiamin (vitamin B1) deficiency, so targeted nutrition that supports any nutritional deficits can help. Whole grain cereals, legumes (beans and lentils), nuts, lean pork, and yeast are rich sources of thiamin. Those with WKS also need to stop drinking alcohol.

People with amnesia due to head trauma may need surgery to remove blood buildup in the brain. People with encephalitis may need anti-inflammatory medications.

A person can help reduce the risk of amnesia by:

• wearing protective headgear during activities that could result in a brain injury, such as cycling, skating, skiing, or playing contact sports
• getting medical attention if there’s a high fever, stiff neck, or severe headaches, which can be a sign of an infection affecting the brain
• wearing a seatbelt while traveling in a motor vehicle, and never driving while under the influence of alcohol or drugs
• having eyes checked annually to help prevent falls, especially if above the age of 65 years
• exercising regularly to reduce the risk of a stroke
• eating a healthy diet that includes leafy green vegetables and avoids saturated fats to help prevent cardiovascular problems that can contribute to memory problems
• getting psychological treatment or encouraging a friend or loved one to seek treatment if they have experienced trauma

Amnesia often resolves on its own without treatment.

A person should speak with a doctor to determine the reason for their memory loss. The sooner they start treatment, the more successful it is likely to be.

The following are some questions a person may ask a doctor:

• What are the possible causes of my memory loss?
• Could my memory loss be permanent?
• What treatments do you recommend to help restore my memory?
• What tests do you recommend, and how should I prepare for them?
• Will any lifestyle changes be necessary to help get my memory back?

What is the difference between amnesia and dementia?

Amnesia is different from dementia. Dementia includes memory loss. Unlike amnesia, it also involves other important cognitive problems, such as impairments in judgment and abstract thinking, that may affect the person’s ability to carry out daily activities.

Do all types of amnesia have the same symptoms?

Different types of amnesia have different symptoms. For example:

• Anterograde amnesia: A person cannot remember new information but can remember events from before the onset of amnesia.
• Retrograde amnesia: A person can remember new information but cannot remember events from before the onset of amnesia.
• Dissociative amnesia: A person may forget specific events or time periods.
• Traumatic amnesia: After a head injury, a person may experience anterograde amnesia, retrograde amnesia, or both types.

Can a person treat amnesia at home?

A person should speak with a doctor to determine the cause of any unexplained memory loss. A doctor can recommend the best treatment for retrieving memories, such as psychotherapy or hypnosis. There are currently no medications for treating amnesia.