Amnesia

**Amnesia** is what doctors call a loss or disturbance of memory. It affects both long and short term memory. It is a loss of memory, that is to say, a person cannot remember certain things. Amnesia can be caused when someone has brain damage, a disease or when something really stressful happens.

There are two "main types":
*Anterograde amnesia: Short term memory is not transferred to long-term memory any more. People with this type of amnesia cannot remember things for long periods of time.
*Retrograde amnesia: The person can no longer recall information that happened before a certain date. The date is usually the date of an accident or an operation. 

The fact that adults usually cannot remember events that occurred in early childhood is called "infantile amnesia". It is attributed to the development of the brain or that of the child. It is not seen as a form of amnesia comparable to the other types. 

## Causes
There are three main categories in which amnesia can happen to a person.

*Head trauma. This includes any kind of injury to the brain that might cause amnesia. 
*Traumatic events. This happens when a person's mind is so stressed that it chooses to forget what happened rather than to deal with it.
*Physical deficiencies. These are things that happen to your brain but it is different than head trauma because it mostly deals with complications that happen after surgery. 

Some other different types of amnesia include:
*Caused by an injury, for example a head injury, trauma or insult. This is called *post-traumatic amnesia*.
*Dissociative amnesia: When the cause is psychological, and usually not related to physical damage in the brain. This includes
***Repressed memory* (where it is not possible to remember a specific event) - The memory is usually still there, but the person blocks access to it; Stressful events such as being raped may lead to Dissociative amnesia
** *Childhood amnesia* - the inability of adults to remember certain parts of their childhood.
**Drug (usually alcohol)-induced blackout* - anterograde amnesia, affecting the immediate past

Amnesia can be permanent, or it can be temporary. Damage to the brain, or the use of certain drugs can cause amnesia. Some of these drugs are sedatives and hypnotics. Another well known cause for amnesia can be drinking too much alcohol. These kinds of causes are called *organic*, because they can been directly seen. Other causes cannot directly be seen, they are called *functional*.  Rather they are psychologicalin their nature. People may want to shield off a traumatic event they witnessed, for example.

Another minor cause of amnesia is "heartbreak" in a relationship. It can lead to trauma, but it is not necessarily traumatic.

## Treatment
Sometimes certain types of amnesia fix themselves without being treated. There are also different types of therapy that work with the brain to help with amnesia. There is no medicine that can directly help with amnesia.

## Transient global amnesia (TGA)
An incident of TGA can last "one to 10 hours (six hours is average)", before the patient returns to normal with the ability to form new memories. Such incidents have disruptions of short-term memory.