ARTICLE

Amnesia (Fig. 1) has been defined as ‘an abnormal mental state in which memory and learning are affected out of all proportion to other cognitive functions in an otherwise alert and responsive patient ’ (Victor 1971). Memory impairment can affect the learning of new material (anterograde amnesia), owing to impairments in the encoding, storage or retrieval stages. It can also affect the recall of previously acquired memories (retrograde amnesia), which might involve personal experiences (episodic memory), general information (semantic memory) or perceptuomotor skills (procedural memory). Psychological factors can cause both anterograde and retrograde memory loss (or a combination of the two). Types of psychogenic amnesia Psychologically based amnesia includes the persistent anterograde memory impairment present in mental disorders such as depression, which in an extreme form can lead to depressive pseudodementia. Alternatively, it can cause transient or discrete episodes of retrograde and/or anterograde memory loss, which we refer to here as ‘psychogenic ’ amnesia (i.e. loss not due to identifiable brain disease). Why ‘psychogenic’? A number of terms have been used to describe medically unexplained amnesia, including ‘hysterical’, ‘psychogenic’, ‘dissociative ’ and ‘functional’. Each requires the exclusion of an underlying neurological cause and the identification of a precipitating stress that has resulted in amnesia. Unfor tunately, the presence of amnesia may make it difficult to identify the stress until either informants have come forward or the amnesia itself has resolved