Generalities:

Amnesia is a disorder in the function of memory.

Amnesia can be organic, that is, for physiological reasons such as injury, illness or drug abuse.

Functional amnesia is given as a psychological defense mechanism.

Amnesia can also be transient, spontaneous or selective. When the loss of memory is due to the deterioration of the brain, it can be Alzheimer's and can be part of senile dementia.