query: How long can amnesia last?
passage: Amnesia
Amnesia is a deficit in memory caused by brain damage, disease, or psychological trauma.[1] Amnesia can also be caused temporarily by the use of various sedatives and hypnotic drugs. The memory can be either wholly or partially lost due to the extent of damage that was caused.[2] There are two main types of amnesia: retrograde amnesia and anterograde amnesia. Retrograde amnesia is the inability to retrieve information that was acquired before a particular date, usually the date of an accident or operation.[3] In some cases the memory loss can extend back decades, while in others the person may lose only a few months of memory. Anterograde amnesia is the inability to transfer new information from the short-term store into the long-term store. People with this type of amnesia cannot remember things for long periods of time. These two types are not mutually exclusive; both can occur simultaneously.
passage: Post-traumatic amnesia
2–12 weeks – the injury is very severe, and recovery is likely to take a year or more. The patient is likely to exhibit permanent deficits in memory and cognitive function, and the patient is unlikely to be able to return to work.