The most common causes of amnesia – which refers to an abnormally severe loss or failure of memory – are stroke, head injury, illness (i.e. dementia), or poisoning. However, amnesia has also been known to be triggered by sudden and intense bouts of extreme stress and/or emotional trauma.
Medical science has identified many different types of amnesia, largely defined by the specific presentation of their symptoms.
For example, Retrograde Amnesia refers to a loss of memory for previous events (usually confined to a brief period just preceding the damage and only in rare cases resulting in more widespread memory loss), while Anterograde Amnesia refers to an inability to form new memories after the initial onset/cause.
Amnesia is the inability to recall past events. Amnesia can result from physical trauma (such as being in an accident and getting a blow to the head) or from psychological problems. One type of amnesia, dissociative amnesia, is the inability to recall events that results from psychological problems, specifically from too much stress. This is sometimes seen in victims of horrible events such as violent crimes, murder, war, etc. It is not a typical situation, but sometimes when an event is simply too difficult for a person to handle, they protect themselves by blocking the memory of the event. In these cases the problem is usually temporary.