Amnestic disorders are characterized by memory impairment resulting from drug abuse, a side-effect of medication, or from exposure to a toxin, although cases of amnesia exist without specific etiology.
A person with an amnestic disorder always experiences levels of impairment in their ability to learn and retain new information. Some people with amnestic disorders might be unable to recall information previously learned, but this is more variant than the ability to retain new information and depends on the location and severity of brain damage.
The severity of memory disturbance impairs the person socially and/or occupationally, and marks decline in level of functions. The memory impairment should not occur exclusively during the course of delirium or dementia in order to be diagnosed as an amnestic disorder. In some cases, the person may vividly recall experiences of the distant past with no recollection of more current occurrences.
The ability to access sequential strings of information is typically not effected, such as counting and reciting the alphabet. Amnestic disorders are often associated with features such as confusion and disorientation. Confabulation, imaginative information developed to fill in the gaps of memory, is not uncommon in the initial stages of treatment, but does tend to wane with time. Because confabulation is a factor to be mindful of during the treatment process, its important to collaborate with the client's family and other informants to collect accurate data about the individual and his or her life.
Those with severe amnestic disorders often have lack of insight into their deficiencies, which can result in agitation upon confrontation.